The best answers are your own. Try different pressures, for a tank, calculate your mpg, see how the ride feels. 15" higher profile tires vs 17" low profile. that too is a factor: I find less upside to higher-than-spec pressures with 17". Still exceed, but just a nominal amount. I gave up on front/rear psi differences, just set them all the same, as much for expedience when (DIY) rotating as anything.
