So I'm pretty impressed with FRP/extruded foam panels and fiberglass pultrusions- strong, non-corrosive, great thermal properties, etc. In fact, given the samples we've put together, I'm considering going from a 2" OD to 1.5" OD for the wall/vertical panels. I'll lose a little bit of insulation, but I'll save a lot of weight (mainly on the exterior extrusions by being able to go from a 4"x4" angle to a 3"x3" angle). The materials for the basic shell (including slideout) are still coming in under 2500lbs, which is very cool.
I'm hoping to make my decision on vendors this week, then order the panels and pultrusions. It will take about 4 weeks for everything to be manufactured and shipped to Utah, and I'm guessing another 4 weeks for the basic body to be assembled.
I'm toying with the idea of building a little cargo trailer out of fiberglass structural components and panels to match the camper. In fact, I might have that done first as an assembly "warm-up", to get a little experience with the materials.