I asked similar questions see "Suspension mods for RVing ideas?" MY truck is f350 cc 4X4 with stock suspension and tires, 28' Cimarron 5th wheel with flipped axles and I still have clearance issues appx 2" at the tailgate with the trailer setting level when hitched. Who makes the king pin box extenders to get more tail gate to trailer apron clearance? I could simply lower the pin but I dont want to upset the trailer suspension with taildragging. Same issue but cant remove rear end leafs because I pull different equip that requires the unmodded suspension on the truck. Help!!!!