Jared- we run on a medium traction p/l, and I have found the exact same thing you found- as the track gets really hot, the traction compound quits working.
Try this: when the track temp get on up there, instead of letting the traction compound sit on the tires, put it on, wait a few seconds, then wipe it right off. You are basically doing the same thing- just cleaning them, but you are also putting a little compound into the outside skin of the tire. If you let them sit with compound on them (in the heat), you will have one greasy, skating, donut cutting ride! lol