diff --git a/SabreTools.DatFiles/DatFile.FromMetadata.cs b/SabreTools.DatFiles/DatFile.FromMetadata.cs
index 9fd8efdd..b8a5161c 100644
--- a/SabreTools.DatFiles/DatFile.FromMetadata.cs
+++ b/SabreTools.DatFiles/DatFile.FromMetadata.cs
@@ -1064,20 +1064,21 @@ namespace SabreTools.DatFiles
 
                 var item = new DatItems.Formats.Rom();
                 item.SetName(name);
-                item.SetFieldValue<string?>(Models.Metadata.Rom.OffsetKey, rom.ReadString(Models.Metadata.Rom.OffsetKey));
+                item.SetFieldValue<string?>(Models.Metadata.Rom.OffsetKey, rom.ReadString(Models.Metadata.Rom.StartKey));
                 item.SetFieldValue<string?>(Models.Metadata.Rom.OpenMSXMediaType, subType.AsStringValue());
-                item.SetFieldValue<string?>(Models.Metadata.Rom.OpenMSXType, rom.ReadString(Models.Metadata.Rom.OpenMSXType));
+                item.SetFieldValue<string?>(Models.Metadata.Rom.OpenMSXType, rom.ReadString(Models.Metadata.Rom.OpenMSXType) ?? rom.ReadString(Models.Metadata.Rom.TypeKey));
                 item.SetFieldValue<string?>(Models.Metadata.Rom.RemarkKey, rom.ReadString(Models.Metadata.Rom.RemarkKey));
                 item.SetFieldValue<string?>(Models.Metadata.Rom.SHA1Key, rom.ReadString(Models.Metadata.Rom.SHA1Key));
+                item.SetFieldValue<string?>(Models.Metadata.Rom.StartKey, rom.ReadString(Models.Metadata.Rom.StartKey));
                 item.SetFieldValue<DatItems.Source?>(DatItems.DatItem.SourceKey, new DatItems.Source { Index = indexId, Name = filename });
 
-                if (dump.Read<Models.OpenMSX.Original>(Models.Metadata.Dump.OriginalKey) != null)
+                if (dump.Read<Models.Metadata.Original>(Models.Metadata.Dump.OriginalKey) != null)
                 {
-                    var original = dump.Read<Models.OpenMSX.Original>(Models.Metadata.Dump.OriginalKey)!;
+                    var original = dump.Read<Models.Metadata.Original>(Models.Metadata.Dump.OriginalKey)!;
                     item.SetFieldValue<DatItems.Formats.Original?>("ORIGINAL", new DatItems.Formats.Original
                     {
-                        Value = original.Value.AsYesNo(),
-                        Content = original.Content,
+                        Value = original.ReadBool(Models.Metadata.Original.ValueKey),
+                        Content = original.ReadString(Models.Metadata.Original.ContentKey),
                     });
                 }
 
diff --git a/SabreTools.DatFiles/DatFile.ToMetadata.cs b/SabreTools.DatFiles/DatFile.ToMetadata.cs
index 21578d40..f7c72c88 100644
--- a/SabreTools.DatFiles/DatFile.ToMetadata.cs
+++ b/SabreTools.DatFiles/DatFile.ToMetadata.cs
@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using SabreTools.Core;
 using SabreTools.Core.Tools;
 
 namespace SabreTools.DatFiles
@@ -557,6 +558,94 @@ namespace SabreTools.DatFiles
         {
             var romItem = item.GetInternalClone();
 
+            // Create a Dump for every Rom that has a subtype
+            switch (romItem.ReadString(Models.Metadata.Rom.OpenMSXMediaType).AsEnumValue<OpenMSXSubType>())
+            {
+                case OpenMSXSubType.Rom:
+                    var dumpRom = new Models.Metadata.Dump();
+                    var rom = new Models.Metadata.Rom();
+
+                    rom[Models.Metadata.Rom.NameKey] = romItem.ReadString(Models.Metadata.Rom.NameKey);
+                    rom[Models.Metadata.Rom.OffsetKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+                    rom[Models.Metadata.Rom.OpenMSXType] = romItem.ReadString(Models.Metadata.Rom.OpenMSXType);
+                    rom[Models.Metadata.Rom.RemarkKey] = romItem.ReadString(Models.Metadata.Rom.RemarkKey);
+                    rom[Models.Metadata.Rom.SHA1Key] = romItem.ReadString(Models.Metadata.Rom.SHA1Key);
+                    rom[Models.Metadata.Rom.StartKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+
+                    dumpRom[Models.Metadata.Dump.RomKey] = rom;
+
+                    var romOriginal = romItem.Read<DatItems.Formats.Original>("ORIGINAL");
+                    if (romOriginal != null)
+                    {
+                        var newOriginal = new Models.Metadata.Original
+                        {
+                            [Models.Metadata.Original.ValueKey] = romOriginal.Value.FromYesNo(),
+                            [Models.Metadata.Original.ContentKey] = romOriginal.Content,
+                        };
+                        dumpRom[Models.Metadata.Dump.OriginalKey] = newOriginal;
+                    }
+
+                    EnsureMachineKey<Models.Metadata.Dump?>(machine, Models.Metadata.Machine.DumpKey);
+                    AppendToMachineKey(machine, Models.Metadata.Machine.DumpKey, dumpRom);
+                    break;
+
+                case OpenMSXSubType.MegaRom:
+                    var dumpMegaRom = new Models.Metadata.Dump();
+                    var megaRom = new Models.Metadata.Rom();
+
+                    megaRom[Models.Metadata.Rom.NameKey] = romItem.ReadString(Models.Metadata.Rom.NameKey);
+                    megaRom[Models.Metadata.Rom.OffsetKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+                    megaRom[Models.Metadata.Rom.OpenMSXType] = romItem.ReadString(Models.Metadata.Rom.OpenMSXType);
+                    megaRom[Models.Metadata.Rom.RemarkKey] = romItem.ReadString(Models.Metadata.Rom.RemarkKey);
+                    megaRom[Models.Metadata.Rom.SHA1Key] = romItem.ReadString(Models.Metadata.Rom.SHA1Key);
+                    megaRom[Models.Metadata.Rom.StartKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+
+                    dumpMegaRom[Models.Metadata.Dump.MegaRomKey] = megaRom;
+
+                    var megaRomOriginal = romItem.Read<DatItems.Formats.Original>("ORIGINAL");
+                    if (megaRomOriginal != null)
+                    {
+                        var newOriginal = new Models.Metadata.Original
+                        {
+                            [Models.Metadata.Original.ValueKey] = megaRomOriginal.Value.FromYesNo(),
+                            [Models.Metadata.Original.ContentKey] = megaRomOriginal.Content,
+                        };
+                        dumpMegaRom[Models.Metadata.Dump.OriginalKey] = newOriginal;
+                    }
+
+                    EnsureMachineKey<Models.Metadata.Dump?>(machine, Models.Metadata.Machine.DumpKey);
+                    AppendToMachineKey(machine, Models.Metadata.Machine.DumpKey, dumpMegaRom);
+                    break;
+
+                case OpenMSXSubType.SCCPlusCart:
+                    var dumpSccPlusCart = new Models.Metadata.Dump();
+                    var sccPlusCart = new Models.Metadata.Rom();
+
+                    sccPlusCart[Models.Metadata.Rom.NameKey] = romItem.ReadString(Models.Metadata.Rom.NameKey);
+                    sccPlusCart[Models.Metadata.Rom.OffsetKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+                    sccPlusCart[Models.Metadata.Rom.OpenMSXType] = romItem.ReadString(Models.Metadata.Rom.OpenMSXType);
+                    sccPlusCart[Models.Metadata.Rom.RemarkKey] = romItem.ReadString(Models.Metadata.Rom.RemarkKey);
+                    sccPlusCart[Models.Metadata.Rom.SHA1Key] = romItem.ReadString(Models.Metadata.Rom.SHA1Key);
+                    sccPlusCart[Models.Metadata.Rom.StartKey] = romItem.ReadString(Models.Metadata.Rom.StartKey) ?? romItem.ReadString(Models.Metadata.Rom.OffsetKey);
+
+                    dumpSccPlusCart[Models.Metadata.Dump.RomKey] = sccPlusCart;
+
+                    var sccPlusCartOriginal = romItem.Read<DatItems.Formats.Original>("ORIGINAL");
+                    if (sccPlusCartOriginal != null)
+                    {
+                        var newOriginal = new Models.Metadata.Original
+                        {
+                            [Models.Metadata.Original.ValueKey] = sccPlusCartOriginal.Value.FromYesNo(),
+                            [Models.Metadata.Original.ContentKey] = sccPlusCartOriginal.Content,
+                        };
+                        dumpSccPlusCart[Models.Metadata.Dump.OriginalKey] = newOriginal;
+                    }
+
+                    EnsureMachineKey<Models.Metadata.Dump?>(machine, Models.Metadata.Machine.DumpKey);
+                    AppendToMachineKey(machine, Models.Metadata.Machine.DumpKey, dumpSccPlusCart);
+                    break;
+            }
+
             // TODO: Handle DipSwitch in Part inversion
             // TODO: Handle DipSwitch in DataArea inversion
 
diff --git a/SabreTools.DatFiles/Formats/OpenMSX.Writer.cs b/SabreTools.DatFiles/Formats/OpenMSX.Writer.cs
index 5977eba1..f555e4b1 100644
--- a/SabreTools.DatFiles/Formats/OpenMSX.Writer.cs
+++ b/SabreTools.DatFiles/Formats/OpenMSX.Writer.cs
@@ -50,8 +50,12 @@ namespace SabreTools.DatFiles.Formats
                 logger.User($"Writing to '{outfile}'...");
 
                 // TODO: Write out comment prefix somehow
-                var softwaredb = CreateSoftwareDb(ignoreblanks);
-                if (!(new Serialization.Files.OpenMSX().SerializeToFileWithDocType(softwaredb, outfile)))
+                //var softwaredb = CreateSoftwareDb(ignoreblanks);
+
+                // Serialize the input file
+                var metadata = ConvertMetadata(ignoreblanks);
+                var softwaredb = new Serialization.CrossModel.OpenMSX().Deserialize(metadata);
+                if (!(new Serialization.Files.OpenMSX().SerializeToFileWithDocType(softwaredb!, outfile)))
                 {
                     logger.Warning($"File '{outfile}' could not be written! See the log for more details.");
                     return false;
@@ -166,7 +170,7 @@ namespace SabreTools.DatFiles.Formats
                 _ => new Models.OpenMSX.Rom(),
             };
 
-            rom.Start = item.GetStringFieldValue(Models.Metadata.Rom.OffsetKey);
+            rom.Start = item.GetStringFieldValue(Models.Metadata.Rom.StartKey);
             rom.Type = item.GetStringFieldValue(Models.Metadata.Rom.OpenMSXType);
             rom.Hash = item.GetStringFieldValue(Models.Metadata.Rom.SHA1Key);
             rom.Remark = item.GetStringFieldValue(Models.Metadata.Rom.RemarkKey);