Tim/Fordman01 - What type of roads are you traveling on? I didn't see any type of cracking/deforming of the truck bed until I took it many miles off the beaten path. Did you notice a greater amount of porpoising? I was tell the DW about this posting and we both agree that with this truck the camper seems to porpoise more than the last one. I don't have the 5th wheel/gooseneck hitch installed on mine although it does have all the support for it. I wonder how much stiffer it makes the middle of the bed. Where the older model didn't have that support.
Rick - Thanks for sharing your thread on the other forum. Reading through that gave me an idea to change the way I planning to put my plywood support together. Especially after looking at the pictures atchafalaya_man posted of the foam board compressing and the damage to the bottom of his camper. I don't have any deforming on the bottom of my camper, yet. I do agree that the bulk/all of the weight is supported by the box/tub of the camper, and thus putting more pressure on the seams of the bed with any type of roll or porpoising. I know how you feel when a bump or pothole sneaks up on you no matter the speed.
06Fargo - I have Torklift frame mounted tie downs with Happijac shackles. The shackles are as old as the rubber bed mat. I've been talking to the DW about replacing them with Fastguns. She said to put them on the wish list. :/ The Happijac's still work although with a little less spring in the fronts.
All - thanks for all the discussion. It has helped me fine tune my plans to, hopefully, prevent any further damage.