I found this article online that explains in depth how to adjust tire pressures. It's long, but a great read! This site also has info on everything else about handling (springs, anti-roll bars, etc.)
http://www.turnfast.com/tech_handling/handling_pressure
I think I'm going to try 35/35 cold next time. With 39 cold on Sunday, my rear end was coming loose on the tighter corners and lowering it by ~4psi seemed to solve the issue. I checked my pressures when the tires cooled down and I had them at about 33psi F/R after adjustments at the event.