Planet 9

I just started Auto-x'ing my 2008 Cayman-S, on the stock Bridgestones, and would like to know what others feel are the best tires for track days. I'm within 1 second of the fastest Corvettes but you know where I'd like to be! I've heard the Kumho V710 is a good choice, but can't seem to find them in the right sizes for the Cayman-S (265/40-18, 235/40-18). Any thoughts?