A couple of thoughts. First, the time limit idea on preliminary races works. I first saw this done at the 1/2 mile Nazareth Speedway back in the 60's when a two division show of modifieds & novices (sportsman) would draw 125 or more cars. Heats & consis for the 90 or so sportsman would be 8 laps or 15 minutes. I saw a couple of races that had big crashes at the start and, when it couldn't be cleaned up in time, the finishing order was the starting order minus the crashees. It worked very, very well. The racers knew that if they wanted to race for their spots they had to stop all the unneeded BS. Another idea that has been brought up here and works well is limiting the support divisions to no more than two and inviting only the top 20 in points for features only. A program that consists of sprint heats, 1st support feature, sprint B main(s), 2nd support feature, sprint feature moves along very nicely.