To get more precise you can weigh your RV and then use the loading charts given by the tire manufacturer (Here is Michelin's). Typically these charts are where people have derived the lower pressure (I believe I'm also running 70 front, 65 in rear--its hibernating for the winter and I won't be checking for another month or so).
The rears are usually less because of the duallys.
I weighed all four corners of our 25.2, and the recommended pressures matched the specs on the sticker. If you weigh, be sure to load your rig like you would for travel first, including water, fuel and passengers.
Bad decisions make great stories!