Hmmm, sounds a lot like what Hallmark has been doing on their campers for several years now. I am sure they are different products but my Milner LX has sandwich composite walls. one of the things I really like about it is the smooth exterior finish, no aluminum siding and it is so easy to keep clean.
http://www.diabgroup...ions_2_2010.pdf
Actually the XPCamper is very different form a Hallmark.
The XPCamper is a true all composite camper. A seamless build that uses no wood products. The interior uses molds for consistency and weight reduction. I: E Cabinets; rear seat and storage compartment; galley and shower/toilet cabinet.
There is no internal or external metal frame work used as it is the 1st true monocoque design/build in a pop up truck camper.
The XPCamper lends itself to the yacht building industry where composites and molds are used to save weight while allowing superior strength properties; which also achieves a seamless structure which is not possible by using composite panel construction.
By using a foam core; the insulation is already built in place achieving additional weight savings since no other materials are needed. This is one of the advantages by using a foam core over a balsa core; yet more costly to build.
However; when the camper comes out of the mold it is basically a finished unit.
You can read about the construction method here
http://xpcamper.com/design-construction.html
http://www.diabgroup.com/