diff --git a/SabreTools.Models/CHD/Header.cs b/SabreTools.Models/CHD/Header.cs
index 630bf0f..2e97aca 100644
--- a/SabreTools.Models/CHD/Header.cs
+++ b/SabreTools.Models/CHD/Header.cs
@@ -1,21 +1,25 @@
+using System.Runtime.InteropServices;
+
 namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public abstract class Header
     {
         /// <summary>
         /// 'MComprHD'
         /// </summary>
-        public string? Tag { get; set; }
+        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)]
+        public string? Tag;
 
         /// <summary>
         /// Length of header (including tag and length fields)
         /// </summary>
-        public uint Length { get; set; }
+        public uint Length;
 
         /// <summary>
         /// Drive format version
         /// </summary>
-        public uint Version { get; set; }
+        public uint Version;
     }
 }
\ No newline at end of file
diff --git a/SabreTools.Models/CHD/HeaderV1.cs b/SabreTools.Models/CHD/HeaderV1.cs
index 6afaceb..ff73e89 100644
--- a/SabreTools.Models/CHD/HeaderV1.cs
+++ b/SabreTools.Models/CHD/HeaderV1.cs
@@ -1,51 +1,58 @@
-namespace SabreTools.Models.CHD
+using System.Runtime.InteropServices;
+
+namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class HeaderV1 : Header
     {
         /// <summary>
         /// Flags
         /// </summary>
-        public Flags Flags { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public Flags Flags;
 
         /// <summary>
         /// Compression type
         /// </summary>
-        public CompressionType Compression { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public CompressionType Compression;
 
         /// <summary>
         /// 512-byte sectors per hunk
         /// </summary>
-        public uint HunkSize { get; set; }
+        public uint HunkSize;
 
         /// <summary>
         /// Total # of hunks represented
         /// </summary>
-        public uint TotalHunks { get; set; }
+        public uint TotalHunks;
 
         /// <summary>
         /// Number of cylinders on hard disk
         /// </summary>
-        public uint Cylinders { get; set; }
+        public uint Cylinders;
 
         /// <summary>
         /// Number of heads on hard disk
         /// </summary>
-        public uint Heads { get; set; }
+        public uint Heads;
 
         /// <summary>
         /// Number of sectors on hard disk
         /// </summary>
-        public uint Sectors { get; set; }
+        public uint Sectors;
 
         /// <summary>
         /// MD5 checksum of raw data
         /// </summary>
-        public byte[]? MD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[] MD5 = new byte[16];
 
         /// <summary>
         /// MD5 checksum of parent file
         /// </summary>
-        public byte[]? ParentMD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[] ParentMD5 = new byte[16];
     }
 }
diff --git a/SabreTools.Models/CHD/HeaderV2.cs b/SabreTools.Models/CHD/HeaderV2.cs
index aac4134..873633c 100644
--- a/SabreTools.Models/CHD/HeaderV2.cs
+++ b/SabreTools.Models/CHD/HeaderV2.cs
@@ -1,56 +1,63 @@
-namespace SabreTools.Models.CHD
+using System.Runtime.InteropServices;
+
+namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class HeaderV2 : Header
     {
         /// <summary>
         /// Flags
         /// </summary>
-        public Flags Flags { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public Flags Flags;
 
         /// <summary>
         /// Compression type
         /// </summary>
-        public CompressionType Compression { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public CompressionType Compression;
 
         /// <summary>
         /// Seclen-byte sectors per hunk
         /// </summary>
-        public uint HunkSize { get; set; }
+        public uint HunkSize;
 
         /// <summary>
         /// Total # of hunks represented
         /// </summary>
-        public uint TotalHunks { get; set; }
+        public uint TotalHunks;
 
         /// <summary>
         /// Number of cylinders on hard disk
         /// </summary>
-        public uint Cylinders { get; set; }
+        public uint Cylinders;
 
         /// <summary>
         /// Number of heads on hard disk
         /// </summary>
-        public uint Heads { get; set; }
+        public uint Heads;
 
         /// <summary>
         /// Number of sectors on hard disk
         /// </summary>
-        public uint Sectors { get; set; }
+        public uint Sectors;
 
         /// <summary>
         /// MD5 checksum of raw data
         /// </summary>
-        public byte[]? MD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[]? MD5 = new byte[16];
 
         /// <summary>
         /// MD5 checksum of parent file
         /// </summary>
-        public byte[]? ParentMD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[]? ParentMD5 = new byte[16];
 
         /// <summary>
         /// Number of bytes per sector
         /// </summary>
-        public uint BytesPerSector { get; set; }
+        public uint BytesPerSector;
     }
 }
diff --git a/SabreTools.Models/CHD/HeaderV3.cs b/SabreTools.Models/CHD/HeaderV3.cs
index 92af8f7..9b235ab 100644
--- a/SabreTools.Models/CHD/HeaderV3.cs
+++ b/SabreTools.Models/CHD/HeaderV3.cs
@@ -1,56 +1,65 @@
-namespace SabreTools.Models.CHD
+using System.Runtime.InteropServices;
+
+namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class HeaderV3 : Header
     {
         /// <summary>
         /// Flags
         /// </summary>
-        public Flags Flags { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public Flags Flags;
 
         /// <summary>
         /// Compression type
         /// </summary>
-        public CompressionType Compression { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public CompressionType Compression;
 
         /// <summary>
         /// Total # of hunks represented
         /// </summary>
-        public uint TotalHunks { get; set; }
+        public uint TotalHunks;
 
         /// <summary>
         /// Logical size of the data (in bytes)
         /// </summary>
-        public ulong LogicalBytes { get; set; }
+        public ulong LogicalBytes;
 
         /// <summary>
         /// Offset to the first blob of metadata
         /// </summary>
-        public ulong MetaOffset { get; set; }
+        public ulong MetaOffset;
 
         /// <summary>
         /// MD5 checksum of raw data
         /// </summary>
-        public byte[]? MD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[]? MD5 = new byte[16];
 
         /// <summary>
         /// MD5 checksum of parent file
         /// </summary>
-        public byte[]? ParentMD5 { get; set; } = new byte[16];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
+        public byte[]? ParentMD5 = new byte[16];
 
         /// <summary>
         /// Number of bytes per hunk
         /// </summary>
-        public uint HunkBytes { get; set; }
+        public uint HunkBytes;
 
         /// <summary>
         /// SHA1 checksum of raw data
         /// </summary>
-        public byte[]? SHA1 { get; set; } = new byte[20];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
+        public byte[]? SHA1 = new byte[20];
 
         /// <summary>
         /// SHA1 checksum of parent file
         /// </summary>
-        public byte[]? ParentSHA1 { get; set; } = new byte[20];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
+        public byte[]? ParentSHA1 = new byte[20];
     }
 }
diff --git a/SabreTools.Models/CHD/HeaderV4.cs b/SabreTools.Models/CHD/HeaderV4.cs
index 75041dc..069ea60 100644
--- a/SabreTools.Models/CHD/HeaderV4.cs
+++ b/SabreTools.Models/CHD/HeaderV4.cs
@@ -1,51 +1,59 @@
-namespace SabreTools.Models.CHD
+using System.Runtime.InteropServices;
+
+namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class HeaderV4 : Header
     {
         /// <summary>
         /// Flags
         /// </summary>
-        public Flags Flags { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public Flags Flags;
 
         /// <summary>
         /// Compression type
         /// </summary>
-        public CompressionType Compression { get; set; }
+        [MarshalAs(UnmanagedType.U4)]
+        public CompressionType Compression;
 
         /// <summary>
         /// Total # of hunks represented
         /// </summary>
-        public uint TotalHunks { get; set; }
+        public uint TotalHunks;
 
         /// <summary>
         /// Logical size of the data (in bytes)
         /// </summary>
-        public ulong LogicalBytes { get; set; }
+        public ulong LogicalBytes;
 
         /// <summary>
         /// Offset to the first blob of metadata
         /// </summary>
-        public ulong MetaOffset { get; set; }
+        public ulong MetaOffset;
 
         /// <summary>
         /// Number of bytes per hunk
         /// </summary>
-        public uint HunkBytes { get; set; }
+        public uint HunkBytes;
 
         /// <summary>
         /// Combined raw+meta SHA1
         /// </summary>
-        public byte[]? SHA1 { get; set; } = new byte[20];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
+        public byte[]? SHA1 = new byte[20];
 
         /// <summary>
         /// Combined raw+meta SHA1 of parent
         /// </summary>
-        public byte[]? ParentSHA1 { get; set; } = new byte[20];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
+        public byte[]? ParentSHA1 = new byte[20];
 
         /// <summary>
         /// Raw data SHA1
         /// </summary>
-        public byte[]? RawSHA1 { get; set; } = new byte[20];
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
+        public byte[]? RawSHA1 = new byte[20];
     }
 }
diff --git a/SabreTools.Models/CHD/HeaderV5.cs b/SabreTools.Models/CHD/HeaderV5.cs
index dd8c819..c3bfd02 100644
--- a/SabreTools.Models/CHD/HeaderV5.cs
+++ b/SabreTools.Models/CHD/HeaderV5.cs
@@ -1,6 +1,9 @@
-namespace SabreTools.Models.CHD
+using System.Runtime.InteropServices;
+
+namespace SabreTools.Models.CHD
 {
     /// <see href="https://github.com/mamedev/mame/blob/master/src/lib/util/chd.h"/> 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class HeaderV5 : Header
     {
         /// <summary>