I'm so glad I found this thread. I drive for a living and I've been trying to come up with a way for me to be able to camp whenever I get sent out-of-state. Thanks to all of your pictures I've so far been able to build a tri-fold bed platform just like yours. I chose to make it out of 1/2" plywood, and my reinforcements on the sides are simply aluminum C-channel made for 1/2" plywood. I unfold it, slide the C-channel onto the sides and it turns it just as stiff as it was when it was a full sheet of plywood. I also ordered the rain deflectors for my side windows like you did on the first page. Also, a tri-fold memory foam mattress like yours, but mine is 3" instead of 2" like yours.
I just made my solar purchase, and I chose to build my own kit rather than buy one from the manufacturer. I went with the monocrystalline panels from HQST. After doing some dimension measurements, I found you were right about them not fitting with 2 panels. The polycrystalline panels fit perfectly the way you installed them, so I was about to order a set of those when I found some "slim" panels from HQST. They will fit perfectly side by side the "long way" rather than front to back like you installed yours. I also went with a 20 amp charge controller, and I happened to already have two spare 60ah deep cycle AGM batteries lying around.
I think my next purchase will probably be a 12v fan to run while I sleep, and to find some thermal reflector material to put over the windows to keep the heat and light out in the summer. I'm thinking of buying some freezer bags from the grocery store and turning them inside out and cutting them to the size of the windows.
Thanks for spending so much time documenting everything you've done to help others like myself!