Why not open the Pro UTV class up to 1000cc and then let the smaller, older machines be the ones that run sportsman class. Usually the bigger, faster machines are the ones that the serious racers are going to gravitate towards anyway, the smaller, older machines are going to become great machines for newcomers to the sport to buy and run.
Start placing too many restrictions on the bigger cc machines, and those drivers will just end up moving into a buggy or truck class and then UTVs will remain a little time proposition that promoters won't care to deal with. People want to see speed, they want go fast, not go slow... promoters are going to promote what spectators and fans want and sponsors are going to lean towards the faster machines that win...
So, wanna kill the sport, don't let it grow, keep the rules geared to the backyard racers...
BITD, SNORE, SCORE and LOORS are bigtime events, if someone wants to race a tired old 660cc car, there are plenty of amatuer avenues for them to dice it out in.
Corry, wouldn't you agree that the more air your car catches and the faster it goes, the more the crowd responds...that's what promoters want...