...I'm thinking about increasing the strength of the roof by glassing in 1x2s...
I noticed in some of the great photos posted by Fiber Stream
owners (I think Frederick's fan installation was where I first noticed) that there are ribs moulded in across the roof of that design. From the inside, the lines are visible but the surface is basically flat, suggesting that the ribs are created in the mould, then 'glassed over on the inside to form box beams, as Don is proposing (but external, rather than internal). I have no idea what might fill the Fiber Stream
The need for roof reinforcement is increased by the choice of a roof with a large flat area. The Fiber Stream
uses those ribs, some Bigfoot
models use a substantial plywood panel, and I've seen the Shuttle cargo trailer
moulded fiberglass, and I see a lot of them around here) with a small number of steel internal frames (a squared U running across the ceiling and down the walls).