Thanks for the info.
Our trucks have flexy frames, but not as flexy as the bigger HD trucks. I'm banking on some body/cab mounts doing the trick. I didn't want a pivoting mount. I solid mounted a similar camper to a '84 Toyota, and it was fine, but that truck had a torsionally stiffer frame than the new ones. Sure, it's an unknown. But we can drive ourselves crazy worrying about stuff.
Regarding the mount material, the rubber ones I've seen seem to not use inner sleeves which I don't like. But I need to think about this some more. Really need to get the bed off so I can take good measurements and get the mounts sorted.
I considered Carbon Core, but I got some sample pieces with plywood skins not bonded properly, and some forum members had the same issue. FG skins are probably ok in that respect. I decided to make my own panels because I wanted a curved front and top and numerous hard points, and what the hell... I just wanted to try making my own. It'll be well insulated too, with 2" thick XPS. So far I only have the floor/base panel done. I used a layer of 1808 and 1700 biax on that, but the rest will use a double layer of 1700 on the outside and 1700+6oz on the inside.
Have you seen the Super Camper writeup?
http://thesupercamper.blogspot.com/