Are you truly forbidden from racing up a category in cyclocross, or is it more a matter of not being able to earn points in that category? In the few mountain bike races that I've done, no one really cared if you moved up without filing the paperwork... if you got schooled, that was just sort of your problem. It was understood, however, that you couldn't drop back down without good reason. If I decide that I want to race out of my class (group C, cat 4, whatever) half way through the season, do I really have to harass USCF until they send me a new license?