Suspension mods for 2010 Ford F450 4x4 for large camper?

I have a 2008 F-450 and carry a large Lance 1191. The only mod I did to the suspension was to add 2, 3/4" leaves to each side. Truck now rides 4" high when unloaded and squats 4" with the camper on. Drives like there's no load in the rear with the camper on board (although with no load in the rear, it drives like a truck with concrete blocks for tires...) I only off load to get a load of stone, lumber or wood pellets.

John