Fox 35 Combat has been done as well, and can be tons of fun. But there's always 'that guy' who bores out his venturi, does some grinding on the crank port, or some other tweak and is about 20mph faster than everybody else. That's why I like the speed limit idea. Anything goes, as long as you don't exceed XXmph. Skill classes help, too, that way you might be flying against an expert, but you're competing against your peers. The experts have lighter, tighter turning stuff, and a skill set to match, but the beginners are keeping up and learning a thing or two.