No idea here, but an interesting comment. When I was about 12 years old my dad bought a used combined truck and camper. The truck was a 1972 F250 and the camper a 12.5' heavy something or other. The previous owner had CUT SOME METAL OUT of the top surface of the truck frame allowing the bed mount to sit lower into the frame on the left side than the stock height on the right. This also forced the camper lower on the left - only about a quarter inch or so but noticeable after purchase and ownership after a short period of time. Dad had me roll under the truck to see what was going on. We figured the previous owner did this to counteract road crown, maybe at the request of wife or family riding along in back?
Of course that would have weakened the frame right at a hinge point huh?