✅ Marshal.SizeOf is not what I'm thinking

[StructLayout(LayoutKind.Explicit)]
internal unsafe struct ChunkData
{
    public const int CELL_SIZE = 33;
    public const int CELL_LENGTH = CELL_SIZE * CELL_SIZE * CELL_SIZE;
    public const int CELL_BIT_LENGTH = (CELL_SIZE * CELL_SIZE * CELL_SIZE) / 8 + 1;

    public const int SIZE = CELL_LENGTH + CELL_BIT_LENGTH;

    [FieldOffset(0)]
    public fixed byte volumeData[CELL_LENGTH];

    [FieldOffset(CELL_LENGTH)]
    public fixed byte maxCellCache[CELL_BIT_LENGTH];
}

[StructLayout(LayoutKind.Explicit)]
internal unsafe struct ChunkDataBackupWrapper
{
    public const int SIZE = ChunkData.SIZE + 1;

    [FieldOffset(0)]
    public bool hasBeenBacked;

    [FieldOffset(1)]
    public ChunkData chunkData;
}