Haha, my dad and I fiddled with the backs for a good ten minutes trying to make sure I loaded the film right when I got my setup for the first time. It looks almost exactly the same loaded either way, but the way to tell is to make sure the end facing the dark slide is black. If it's yellow/white/whatever color the paper protecting your 120 film is, it's backwards.
Also, artonpaper, I believe the default non-electronic speed is 250th of a second, but I could be mistaken. Anyways, that's the reason I'd prefer to have a Bronica S2a, but they're more expensive.