So the challenge is that you'll get some moisture and dust in your truck bed with a GFC (go fast camper), no matter how much you try to seal the GFC panels and doors. Just accept that and build accordingly. I'm using marine grade Okoume plywood, wrapped in grey coin flooring laminate I got from Home Depot. just goto Home Depot and search for grey coin flooring. I got a roll 25' long and 4' wide. The downside is it's heavy. and getting the adhesive to bond has been a challenge. Contact cement may have been a better choice. First on the plywood i sealed the edges with epoxy. cured epoxy is not uv stable, but I'm wrapping the plywood in the grey coin laminate so no problem; it'll never see the Sun. I also filled the plywood edges with epoxy mixed with wood flour. that did wonders. I then used my narrow 1/4" crown stapler to help fold the grey coin laminate over the edges. Limestone sika flex to fill in any gaps (in the concrete...