Mark,
Did you weigh the coach at each wheel? If not, you do not know what air pressure to run because these coaches can vary over a 1,000 lbs. from one side to the other, and the proper air pressure for an axle is determined by using the heaviest side. So taking the total weight of an axle and dividing it in half does not work. Also the coach needs to be weighted at each wheel as it is used and that includes clothes, food, tools that you carry, full tanks including fuel, and a loaded trailer if you tow one. Until you know you wheel loading, I always recommend that an owner run the maximum air pressure for the tire because an over inflated tire may not ride as well as one properly inflate, an under inflated tire will blowout or receive internal damage that will cause a future failure, and that is an unnecessary safety risk. A blowout usually causes expensive damage if not a wreck that can be very serious.
Gerald