lance camper porpoising and tires cupping

I have had 3 F250's. All have had the camper suspension package with heavier springs in front, and the helper spring in the back. Have airbags on the latest, to bring up the rear with a 2200 lb. aluminum frame camper on back with a 8' bed. Is the Lance Squire Lite a short bed or long bed? The camper package has a rear sway bar. I keep my air bags at 70-80 lbs., The non adjusting billstein shocks I put on feel no different than the stock shocks when new. Also have the high load range tires on at 70 pounds. I do not have 4 x 4, but a 2 x 4. I was told to run the air bags at 10 pounds when there was no load. Fully loaded with 10 pounds in the air bags, would be like having no air bags. I have been very happy with the ride with air bags in our present setup.

When I was new to truck camping, and inexperienced, I had an old 1/2 ton with a home made on back. That combination would bounce like a rubber ball. Driving on 95 in S Carolina was like a carnival ride! I had normal shocks on coil springs. That was a lot of the reason I went to the newer trucks with the camper package suspension. To me it sounds like a combination of things. Not enuf rating tires for the load, low pressure in the air bags, wrong shocks and not enuf springs in the rear. Not familiar with the front I beams in a Ford 4 x 4, but would wonder if stiffer coils would help.