I think the limitation is intended to be one of size, weight AND power. The problem is that the site owner doesn't seem to be up on current cars or they would know that a certain "little Japanese Subaru" is really a big heavy fire-breathing pavement-munching "muscle car".
Of course, it IS a MINI club event. Makes sense that they wouldn't want a bunch of cars that are WAY faster than them at their event. (in addition to the embarassment factor, it's a logistical problem... this kind of event works better when all the cars are capable of similar speeds)
Andrew, I'll collect some contact info (I knew where to get that info, anyway), but I'm not sure OGP is where we want to run a "NASA-X Tampa" event. I don't think we'd get enough of our members to make that trip for it to be worthwhile. It's a little too far away for most people.