My Polara runs 9.90s so even though I am too lazy to get a license, it has a diaper. The challenger runs 11.50s and I would run one if I wasn't worried about oil temp on the street. Don't know if that would be an issue or not.

Rather than requiring it on 10.00-11.99 cars, why not give racers incentives to run one? Whether it's an extra run on a t&t day, or even money incentives. I was told that a racer at a track here in MD paid the next entry fee for a racer who wasn't required to have a diaper but had one anyway and ended up grenading a motor. Costs the track more than that to clean it up, so it seems like a good idea.