Hey, you should check out the AMA. Its an organization whos members are model aircraft designers, builders, and flyers. It *effectively* regulates model aircraft activity through its insurance process and it in fact, *does* limit model aircraft to 25 kilos (actually 55 lbs) and also *effectively* requires a "license" for model aircraft larger than that. It has about 300,000 members - almost as many as the Aircraft Owners and Pilots Association (AOPA) and many more than the Airline Pilots Association (ALPA).

The FAA seems to use that 55 lb limit a lot. I wonder where they got that number? Hey, maybe they actually talk with the AMA about things like that?!?