The idea that you can't spray hyper pistons is a fantasy. You do have to have your top ring gap way wide though. By the same token, if your tune-up is off even forged pistons will suffer thermal events.
I sprayed mine at 150 for a whole pile of runs and never had issues. 175 was a different story, but that was because my setup was fuel rich. I lifted top ring lands twice. Fuel rich is just as bad as nitrous rich.
One thing you have to remember when spraying a lot is that you can't snap the throttle shut on it, you have to drive out of it and let the fuel clear out of the cylinders or it collects in the top lands and ignites.
Not sure how much anyone else sprayed, but I know Mike and Blaine experimented at 225 for sure, and maybe 250.
Best advice I can give you is start small and don't get greedy. Nitrous is very unforgiving if you are off on your tune.
On true street tires 100 or so will be about your limit. Radial T/A's held mine at 75, but they weren't happy at 100 much.
