I have a fiberglass exterior Winnebago Minnie-Winnie with delaminated wall panels. The construction (Laminated panels) process is where the inside panelling is glued to the Styrofoam core and then an exterior layer of wood panelling is glued to the Styrofoam core and then the fiberglass shell is then glued to the outer wood panel to make one very solid panel much like plywood is constructed. they all support one another for strength. Precise metal strips are inserted between the layers where ever interior furniture is scheduled to be screwed into the wall. That's how Winnebago does it, Fleet-wood does something very similar I think The downside is that if you ever get moisture in between the fiberglass and the Styrofoam say from a leaky roof, window, antenna or roof-air (which does happen) you can not get the water out, it is permanently trapped and it warps and decays the wood panel layer and delaminates (separation) the fiberglass siding resulting in large sagging bubbles in your siding and unlike in a conventional home, repair seems impossible, you can not remove the siding to get to the damaged wood because it is all glued together. AAARGH!!! You don't even know you have/had water in the walls until the damage is done. Question then, is if anybody knows how to repair or re-laminate these bubbles? can glue be injected somehow?