I am fully aware that this thread started as a metal approach to an RV. I think this video provides valuable perspective. I have seen thousands American and European builds. Forest builds one a year and sells them for about $69k. It is one of the nicest, practical builds that I have seen. It is simple, elegant, and has a lot of windows real estate. You don't feel so boxed in. I met him and toured his rig at the East Overlanding Expo. He uses a composite of wood, foam, and epoxy. He uses the West System I believe. They make large boats with it. I have used it. It is unbelievably strong if you know what you are doing.