I'm with the folks who recommend spring loaded tie downs. I would never use chains and basic turnbuckles because of the direct pressure of the truck bed twisting against the "solid" camper, as mentioned.
We've had TCs for about 40 years and I've always kept the front spring loaded tie downs tight, with some give still left in the springs, and the rear tie downs fairly loose. I don't know if this is right or wrong, but it's worked well for us over a lot of years and about 300k miles on all sorts of terrain.
1994 26' Fleetwood Flair, 454 TBI.
1994 30' Monaco Dynasty, 5.9 230 HP Cummins, MD 3060, 1992 Geo Tracker.