back from the tracks:
tried 1 set of Sorex 40R's. Believe it or not I think I have more traction than sorex 36R. After 7 runs, the tyres are really worn and you can already see ridges. I'll post a pic later.
Track temperatures ranged from blazing hot to cloudy, but I stuck with the same set with rotations on each wheel.
I have lap times which are better than what i get for 36R, but i made some minor changes to the setups so it's not comparable.