Jefe hit the nail on the head.
I bounced the **** out of my Jayco, and before that a Four Wheel Camper. Both held up great. My Alpenlite had some cab over flex where the cabover attached to the body of the camper. I never could tell if it was a manufacturing or design flaw or if I bounced the Alpenlite on too many rough roads. Perhaps the N-S bed put too much stress on the frame.
The truck is the weak link. Get the right truck and don't sweat the camper.
Keep the camper in the bed, AND, get an E-W bed not a N-S bed and you will be fine regardless of when one you go with.