Just a little history, perhaps, of those fiberglass pieces.
In the early to mid-1970's the company that I worked for (the New Holland farm equipment division of Sperry Corporation) purchased a small company located in Lebanon, OH that I believe may have made that fiberglass.
The company made fiberglass produce tables for grocery stores and made 3-wheeled ATV's, among other products, including that fiberglass for Airstream as I recall.
I had also heard from somebody in our company at that time that this added structural integrety to the Airstreams, but you know I don't think I ever saw one in actual use.
It's a small world when you actually stop to think of it, isn't it? There was Sperry Corporation, with it's Univac Computer Division (world's first computer), and it's New Holland Division (world's first automatic farm hay baler) making parts for Airstream (one of world's first and foremost travel trailer's). I never thought back in the 1970's that I would someday own one of those Airstreams.