We have full backwards compatibility, but the "preferred" method is to use the standard files with the correct extensions. It's completely up to the Application how it reads in the files. The same goes for EOL markers, OSX will read the standard, Mac, Unix or Windows formats, if the App makes use of the correct calls. There is a LOT of confusion in this area with Content for Poser, and I still haven't found an OSX answer. Are the 2 versions of Poser now File compatible? I don't know about others but I'm not buying content because I don't know which version to buy. If I buy the Mac version, it's OS9 and a real pain to convert to OSX, if it's Win and they use an .exe "Installer" then the installer won't run, even if the files are compatible. Sadly the Mac Compatibility FAQ over at the Mac Forum is still OS9 centric and promotes products that aren't available on OSX.