Currently my file is in DropBox...and my assistant occationally accesses the file.
That can be dangerous to your data ust in FileMaker Pro--let alone using GO. If you and your assitant open the drop box located file at the same time (or nearly so), then save the file back to drop box and saves happen automatically with Filemaker during regular use, each save can overwrite any changes made by the other user.
You may want to look at one of the 3rd party synch tools produced for synchronizing data between GO and Pro. Both 360Works and SeedCode offer such products.