I think the plexi is about the same density as wood.

The grant is in progress for two more. The next ones will be framed in aluminum extrusions--like the trailer bed itself-- and sheathed in Coroplast. Top will remain wood so we can screw stuff to it.

As for the solar, still to early to have used it much. So no real data as yet.

As for the ones on the roof of the library, averaged out over the full year, we make about 50% of the electricity we consume. It would be higher except that the panels were deliberately installed at only a two-degree angle, in order to test how bad a bad installation can make it. Not only are they too flat for the angle of the sun, but they don't shed snow in the winter. They are getting good data from that installation.