1. I've run Mod Pan at approx 70 and soft tires did not explode. I've also seen shots of Mod Pan with speed gun at end of straight showing 70+ and no tires explode - Greens/Pinks. Harder tires should be fine at higher speeds.
Actually, I have seen one tire disintegrate - but I forgot to get the glue all around on the inside. . .
2. ajg - I won't trust a speedo mounted on the car. Before I believe you, I'll want to see it measured by some external agency like a radar gun (get a nice local cop) or a measured distance with timer, both recognized speed measuring methods.
Measured distance - show, in video, measuring of 150 feet. Get two electronic door chime things (like from Rad Shack) and use them as a trigger for a stopwatch. It's not too difficult a project and would be cool. . .
Then it just takes a little algebra to convert to MPH or KPH.
But measuring it on axle or wheel doesn't account for tirespin - which is why they don't use it in NHRA. . .