Chris - Great thread! I just stumbled on to it. Obviously we have been talking about it and I think you are on the right track as far as trying to find a better way. You just can't compete with the guys w/ the unlimited amount of tires. Good luck! Why don't you get a big group of guys from the track go in on some foam from BSR and pool the money together and get a discount? The one guy said you could use the rear 1/10th scale foams and make 2pr. out of them. It seems like there are a lot of options, but all of this research costs money and that is what you are trying to save! The only true way to make this work is to find a supplier in Asia, or Hong Kong and start a distributership. This is basically what speedmind has done, but there product is not as good as the other brands. Anyway good job at trying to come up with a solution and I hope you do, this is a very important issue. This is part of the reason why I don't race carpet anymore. With offroad I can use a set of tires for more than half a season!
P.S. Have you talked w/ Bud at all about this, he may be able to help or offer some suggestion. I know he has a line of foam tires for his cars.