I have followed the 10% rule for tire pressure ever since I can remember (hot tire pressure should be 10% higher than cold) but lately I've read about 10/20 rule, 10% difference front, 20% rear. What is everybody running for stock sized tires? I've seen suggestions for 36-38 for rear tire but that's quite a bit lower than factory recommended 42...not so sure I'm interested in changing tires out every couple thousand miles.