diff --git a/SabreTools.DatFiles/DatHeader.cs b/SabreTools.DatFiles/DatHeader.cs
index 7e80045b..f7e3bf13 100644
--- a/SabreTools.DatFiles/DatHeader.cs
+++ b/SabreTools.DatFiles/DatHeader.cs
@@ -213,80 +213,123 @@ namespace SabreTools.DatFiles
         /// <param name="datHeader">DatHeader to get the values from</param>
         public void ConditionalCopy(DatHeader? datHeader)
         {
+            // If the header is invalid, we can't do anything
             if (datHeader == null)
                 return;
 
+            // Convert subheader values
+            if (datHeader._internal.ContainsKey(Models.Metadata.Header.CanOpenKey))
+            {
+                var canOpen = datHeader.GetFieldValue<Models.OfflineList.CanOpen>(Models.Metadata.Header.CanOpenKey);
+                if (canOpen?.Extension != null)
+                    SetFieldValue<string[]?>(Models.Metadata.Header.CanOpenKey, canOpen.Extension);
+            }
+            if (datHeader._internal.ContainsKey(Models.Metadata.Header.ImagesKey))
+            {
+                var images = datHeader.GetFieldValue<Models.OfflineList.Images>(Models.Metadata.Header.ImagesKey);
+                SetFieldValue<Models.OfflineList.Images?>(Models.Metadata.Header.ImagesKey, images);
+            }
+            if (datHeader._internal.ContainsKey(Models.Metadata.Header.InfosKey))
+            {
+                var infos = datHeader.GetFieldValue<Models.OfflineList.Infos>(Models.Metadata.Header.InfosKey);
+                SetFieldValue<Models.OfflineList.Infos?>(Models.Metadata.Header.InfosKey, infos);
+            }
+            if (datHeader._internal.ContainsKey(Models.Metadata.Header.NewDatKey))
+            {
+                var newDat = datHeader.GetFieldValue<Models.OfflineList.NewDat>(Models.Metadata.Header.NewDatKey);
+                SetFieldValue<Models.OfflineList.NewDat?>(Models.Metadata.Header.NewDatKey, newDat);
+            }
+            if (datHeader._internal.ContainsKey(Models.Metadata.Header.SearchKey))
+            {
+                var search = datHeader.GetFieldValue<Models.OfflineList.Search>(Models.Metadata.Header.SearchKey);
+                SetFieldValue<Models.OfflineList.Search?>(Models.Metadata.Header.SearchKey, search);
+            }
+
+            // Selectively set non-standard fields
             if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(DatHeader.FileNameKey)))
-                SetFieldValue<string?>(DatHeader.FileNameKey,
-                    datHeader.GetStringFieldValue(DatHeader.FileNameKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.NameKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.NameKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.NameKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.DescriptionKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.DescriptionKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.DescriptionKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.RootDirKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.RootDirKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.RootDirKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.CategoryKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.CategoryKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.CategoryKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.VersionKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.VersionKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.VersionKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.DateKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.DateKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.DateKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.AuthorKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.AuthorKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.AuthorKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.EmailKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.EmailKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.EmailKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.HomepageKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.HomepageKey,
-                datHeader.GetStringFieldValue(Models.Metadata.Header.HomepageKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.UrlKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.UrlKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.UrlKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.CommentKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.CommentKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.CommentKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.HeaderKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.HeaderKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.HeaderKey));
-
-            if (!string.IsNullOrEmpty(datHeader.GetStringFieldValue(Models.Metadata.Header.TypeKey)))
-                SetFieldValue<string?>(Models.Metadata.Header.TypeKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.TypeKey));
-
-            if (datHeader.GetStringFieldValue(Models.Metadata.Header.ForceMergingKey).AsEnumValue<MergingFlag>() != MergingFlag.None)
-                SetFieldValue<string?>(Models.Metadata.Header.ForceMergingKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.ForceMergingKey).AsEnumValue<MergingFlag>().AsStringValue());
-
-            if (datHeader.GetStringFieldValue(Models.Metadata.Header.ForceNodumpKey).AsEnumValue<NodumpFlag>() != NodumpFlag.None)
-                SetFieldValue<string?>(Models.Metadata.Header.ForceNodumpKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.ForceNodumpKey).AsEnumValue<NodumpFlag>().AsStringValue());
-
-            if (datHeader.GetStringFieldValue(Models.Metadata.Header.ForcePackingKey).AsEnumValue<PackingFlag>() != PackingFlag.None)
-                SetFieldValue<string?>(Models.Metadata.Header.ForcePackingKey,
-                    datHeader.GetStringFieldValue(Models.Metadata.Header.ForcePackingKey).AsEnumValue<PackingFlag>().AsStringValue());
-
+                SetFieldValue<string?>(DatHeader.FileNameKey, datHeader.GetStringFieldValue(DatHeader.FileNameKey));
             if (datHeader.GetFieldValue<DatFormat>(DatHeader.DatFormatKey) != 0x00)
-                SetFieldValue<DatFormat>(DatHeader.DatFormatKey,
-                    datHeader.GetFieldValue<DatFormat>(DatHeader.DatFormatKey));
+                SetFieldValue<DatFormat>(DatHeader.DatFormatKey, datHeader.GetFieldValue<DatFormat>(DatHeader.DatFormatKey));
+
+            // Selectively set all possible fields -- TODO: Figure out how to make this less manual
+            if (GetStringFieldValue(Models.Metadata.Header.AuthorKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.AuthorKey, datHeader.GetStringFieldValue(Models.Metadata.Header.AuthorKey));
+            if (GetStringFieldValue(Models.Metadata.Header.BiosModeKey).AsEnumValue<MergingFlag>() == MergingFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.BiosModeKey, datHeader.GetStringFieldValue(Models.Metadata.Header.BiosModeKey).AsEnumValue<MergingFlag>().AsStringValue());
+            if (GetStringFieldValue(Models.Metadata.Header.BuildKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.BuildKey, datHeader.GetStringFieldValue(Models.Metadata.Header.BuildKey));
+            if (GetStringFieldValue(Models.Metadata.Header.CategoryKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.CategoryKey, datHeader.GetStringFieldValue(Models.Metadata.Header.CategoryKey));
+            if (GetStringFieldValue(Models.Metadata.Header.CommentKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.CommentKey, datHeader.GetStringFieldValue(Models.Metadata.Header.CommentKey));
+            if (GetStringFieldValue(Models.Metadata.Header.DateKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.DateKey, datHeader.GetStringFieldValue(Models.Metadata.Header.DateKey));
+            if (GetStringFieldValue(Models.Metadata.Header.DatVersionKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.DatVersionKey, datHeader.GetStringFieldValue(Models.Metadata.Header.DatVersionKey));
+            if (GetBoolFieldValue(Models.Metadata.Header.DebugKey) == null)
+                SetFieldValue<bool?>(Models.Metadata.Header.DebugKey, datHeader.GetBoolFieldValue(Models.Metadata.Header.DebugKey));
+            if (GetStringFieldValue(Models.Metadata.Header.DescriptionKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.DescriptionKey, datHeader.GetStringFieldValue(Models.Metadata.Header.DescriptionKey));
+            if (GetStringFieldValue(Models.Metadata.Header.EmailKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.EmailKey, datHeader.GetStringFieldValue(Models.Metadata.Header.EmailKey));
+            if (GetStringFieldValue(Models.Metadata.Header.EmulatorVersionKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.EmulatorVersionKey, datHeader.GetStringFieldValue(Models.Metadata.Header.EmulatorVersionKey));
+            if (GetStringFieldValue(Models.Metadata.Header.ForceMergingKey).AsEnumValue<MergingFlag>() == MergingFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.ForceMergingKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ForceMergingKey).AsEnumValue<MergingFlag>().AsStringValue());
+            if (GetStringFieldValue(Models.Metadata.Header.ForceNodumpKey).AsEnumValue<NodumpFlag>() == NodumpFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.ForceNodumpKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ForceNodumpKey).AsEnumValue<NodumpFlag>().AsStringValue());
+            if (GetStringFieldValue(Models.Metadata.Header.ForcePackingKey).AsEnumValue<PackingFlag>() == PackingFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.ForcePackingKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ForcePackingKey).AsEnumValue<PackingFlag>().AsStringValue());
+            if (GetBoolFieldValue(Models.Metadata.Header.ForceZippingKey) == null)
+                SetFieldValue<bool?>(Models.Metadata.Header.ForceZippingKey, datHeader.GetBoolFieldValue(Models.Metadata.Header.ForceZippingKey));
+            if (GetStringFieldValue(Models.Metadata.Header.HeaderKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.HeaderKey, datHeader.GetStringFieldValue(Models.Metadata.Header.HeaderKey));
+            if (GetStringFieldValue(Models.Metadata.Header.HomepageKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.HomepageKey, datHeader.GetStringFieldValue(Models.Metadata.Header.HomepageKey));
+            if (GetStringFieldValue(Models.Metadata.Header.IdKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.IdKey, datHeader.GetStringFieldValue(Models.Metadata.Header.IdKey));
+            if (GetStringFieldValue(Models.Metadata.Header.ImFolderKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.ImFolderKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ImFolderKey));
+            if (GetBoolFieldValue(Models.Metadata.Header.LockBiosModeKey) == null)
+                SetFieldValue<bool?>(Models.Metadata.Header.LockBiosModeKey, datHeader.GetBoolFieldValue(Models.Metadata.Header.LockBiosModeKey));
+            if (GetBoolFieldValue(Models.Metadata.Header.LockRomModeKey) == null)
+                SetFieldValue<bool?>(Models.Metadata.Header.LockRomModeKey, datHeader.GetBoolFieldValue(Models.Metadata.Header.LockRomModeKey));
+            if (GetBoolFieldValue(Models.Metadata.Header.LockSampleModeKey) == null)
+                SetFieldValue<bool?>(Models.Metadata.Header.LockSampleModeKey, datHeader.GetBoolFieldValue(Models.Metadata.Header.LockSampleModeKey));
+            if (GetStringFieldValue(Models.Metadata.Header.MameConfigKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.MameConfigKey, datHeader.GetStringFieldValue(Models.Metadata.Header.MameConfigKey));
+            if (GetStringFieldValue(Models.Metadata.Header.NameKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.NameKey, datHeader.GetStringFieldValue(Models.Metadata.Header.NameKey));
+            if (GetStringFieldValue(Models.Metadata.Header.NotesKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.NotesKey, datHeader.GetStringFieldValue(Models.Metadata.Header.NotesKey));
+            if (GetStringFieldValue(Models.Metadata.Header.PluginKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.PluginKey, datHeader.GetStringFieldValue(Models.Metadata.Header.PluginKey));
+            if (GetStringFieldValue(Models.Metadata.Header.RefNameKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.RefNameKey, datHeader.GetStringFieldValue(Models.Metadata.Header.RefNameKey));
+            if (GetStringFieldValue(Models.Metadata.Header.RomModeKey).AsEnumValue<MergingFlag>() == MergingFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.RomModeKey, datHeader.GetStringFieldValue(Models.Metadata.Header.RomModeKey).AsEnumValue<MergingFlag>().AsStringValue());
+            if (GetStringFieldValue(Models.Metadata.Header.RomTitleKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.RomTitleKey, datHeader.GetStringFieldValue(Models.Metadata.Header.RomTitleKey));
+            if (GetStringFieldValue(Models.Metadata.Header.RootDirKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.RootDirKey, datHeader.GetStringFieldValue(Models.Metadata.Header.RootDirKey));
+            if (GetStringFieldValue(Models.Metadata.Header.SampleModeKey).AsEnumValue<MergingFlag>() == MergingFlag.None)
+                SetFieldValue<string?>(Models.Metadata.Header.SampleModeKey, datHeader.GetStringFieldValue(Models.Metadata.Header.SampleModeKey).AsEnumValue<MergingFlag>().AsStringValue());
+            if (GetStringFieldValue(Models.Metadata.Header.SchemaLocationKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.SchemaLocationKey, datHeader.GetStringFieldValue(Models.Metadata.Header.SchemaLocationKey));
+            if (GetStringFieldValue(Models.Metadata.Header.ScreenshotsHeightKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.ScreenshotsHeightKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ScreenshotsHeightKey));
+            if (GetStringFieldValue(Models.Metadata.Header.ScreenshotsWidthKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.ScreenshotsWidthKey, datHeader.GetStringFieldValue(Models.Metadata.Header.ScreenshotsWidthKey));
+            if (GetStringFieldValue(Models.Metadata.Header.SystemKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.SystemKey, datHeader.GetStringFieldValue(Models.Metadata.Header.SystemKey));
+            if (GetStringFieldValue(Models.Metadata.Header.TimestampKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.TimestampKey, datHeader.GetStringFieldValue(Models.Metadata.Header.TimestampKey));
+            if (GetStringFieldValue(Models.Metadata.Header.TypeKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.TypeKey, datHeader.GetStringFieldValue(Models.Metadata.Header.TypeKey));
+            if (GetStringFieldValue(Models.Metadata.Header.UrlKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.UrlKey, datHeader.GetStringFieldValue(Models.Metadata.Header.UrlKey));
+            if (GetStringFieldValue(Models.Metadata.Header.VersionKey) == null)
+                SetFieldValue<string?>(Models.Metadata.Header.VersionKey, datHeader.GetStringFieldValue(Models.Metadata.Header.VersionKey));
         }
 
         #endregion