I'm not sure, but you could always import to GTC and export a TCX file, right? I started late and was travelling a bunch, I've only uploaded rides for about half the stages and was sitting 13th last I looked
Edit: Just uploaded for today and there was an option for FIT files, that's the 500 right? Also an option to use the Garmin Communicator plugin.
Edit again: I hadn't uploaded for 2 days and slipped to 16th.
Huh, maybe they added it later.