Hi Mike,
I have found that using the recommended pressures + 2 lbs. front and +1 lb. rear works best for me. I usually run 31 lbs. front, 37 lbs. rear on my Boxster with 17" tires (vs. 29/36 standard). I have tried pressures between standard and all the way up to 40 lbs. (COLD) on front and rear, and found the most consistent handling at just a little above the recommended pressures.
Yes, I know I should be checking the tire temps with a pyrometer, but these seem to work for me.
