Thank you for the links logman7777. I keep forgetting to reply but I certainly appreciate it.
Finally some news on the truck camper! I didn't like my FRP siding idea. Exposed screws and joints that I didn't know how to properly seal up made me stop the build. I discovered this material:
Arctic White RV Fiberglass/Filon Siding from RV Parts Nation.
....and it's exactly what I needed. I now have enough to do both sides, the rear, and the front of the cabover. I'm waiting on the bottom and under cabover sections because I'll have some left over after cutting and it's pricey enough to make me wait and see if I can use the extra pieces in these areas. I hope to have new build news soon!
Craig