My 2012 GMC 2500HD D/A crew cab short bed says to run the front tires at 60 and the rear at 70 and that's what I have done for the past three seasons with no problems. Tow a Jayco 26.5 HT RLS and a 19" Crestliner behind the FW with no problems. I see no reason to pump the rear tires, on my truck, up to 80 pounds when the 70 seems to work great.
2012 GMC 2500HD D/A Crewcab
2012 Jayco Eagle SuperLite HT 26.5 RLS
2009 Crestliner Superhawk 1900
2013 Polaris Sportsman 550 EXP
2008 Polaris Sportsman 700 X2