I have a couple of smaller, 30 Watt Renogy solar panels. They measure about 14" x 20". I have wanted some kind of a thin backboard to protect the back surface of the panel. Something to be screwed or zip tied to the back surface of the frame and protect the inner laminated surface from any impacts, rubbing or whatnot. I know these panels are not lightweight, but I've considered having these panels available for hiking or portable use. I've even thought of maybe a couple small sections of stainless piano hinge between the two.

Maybe I should find some thin, quality plywood and paint it. I am thinking some airflow might also be important.

Seems perfect for kydex?  Make a hinge with a series of holes and some rings or cord.

I went to Tap Plastics and got 8mm twin wall polycarbonate greenhouse siding to mount a 130watt semi rigid solar panel to the top of my small camp trailer. The polycarbonate panel is lightweight and the air gap helps with air circulation. They sell it by the foot, so you only have to buy what you need. I used 3m VHB tape to attach the solar panel to the polycarbonate and then the polycarbonate to the trailer. This might be worth looking into for your application?

Or just that corrugated plastic panel used for the outdoor advertising bandit signs on the side of the road... or political signs, which should be pretty easy to find in 3 weeks.