All versions of FM are cross platform.
You only take into account some differences :
Character sets
Characters with ASCII values 0 trough 127 (low ASCII) are the same in both systems.
Characters with ASCII values greater than 127 (high ASCII) may be different, depending on the Win font you're using.
Some Mac high ASCII characters such as the bullet character do not translate properly in Win.
Thus, if you enter text with special characters on your Mac, you may get unexpected results that resuire cleaning up on the PC.
Fonts
TrueType and Adobe fonts are available for both systems. However, you should use the same technology on both computer systems. Otherwise, you're likely to encounter text-aligment problems in the layouts.
Filenames
Mac filenames can have up to 32 characters, but PC filenames can now contain over 200 characters. And filenames in FM 5 and up for Win now end with .fpx extention. Thus, databases that you want users to be able to run on either platform should be named according to the lowest common denominator : 32 characters max. and including .fpx extention.
Colors
Colors are recognized into palettes. Colors are not necessarily mapped the same way on the two systems, so may see strange color effects on the PC when you open a Mac document. However, you can avoid color-related incompatibilities by choosing the 216-color Web palette in the layout section of Application Preferences.
Grafhics formats
FM for Win uses a variety of PC file formats to store pictures. Some of these formats are not supported by Mac. You can, if you want, change this preference setting for any database so FM Win stores all non-portable graphic images in PICT (Mac) format.
GIF, TIFF, JPEG or EPS are compatible across the two platforms.
Printing
Depending on the print driver you use on PC, your PC results may differ from the Mac results, even when using the same printer. You may have to create two versions of each report layout ; one tailored to the PC and the other for Mac.
OLE support
Only Win users can insert or edit OLE objects in FM.
Although Mac users can view, cut, copy, paste OLE objects, they cannot insert or modify them in any way.
Platform-specific capabilities
Several capabilities of the two operating systems are platform-specific; that is, they are available only in Win or only in Mac. If such features are used in designing a script, the script will not run on the other platform.
F.i. Mac only features : AppleTalk support, ability to play Macintosh.snd (sound) files, AppleScript and AppleEvents support.
Win only : Microsoft Registry support, DDE messaging
HTH
John