Duh! I've gotten so used to using Unison that I didn't even think of the obvious.
I only use Windows and Linux (Buying a Mac is on my Someday/Maybe list, however). In the Windows version I don't think that the install gives you an option of where the data is stored. This may be stored in the registry, however, which would make this easy to change. You could also try asking in the GTD_Palm Yahoo! Group, someone else there may know for sure. Personally, I would just play around and see.