Don't know if this is gonna work but going to try and see. An old 8 ft sun shade off my patio. Attached it to the trim rail with 1 screw at each end (this is just a proof of concept test). 12 noon, 85 degrees outside, 87/88 inside. Shade is draped down over fenders and bungied underneath the trailer. If this idea works at all, I'll buy a 12 ft shade with 95% UV blocking. that will let it cover from where this one is attached at rear to just pat the side door toward the front. I'll use a diy pole set up to hold it up when camping. According to the mfg,there is no issue with having attached to the trailer going down the road, or using it horizontally as an awning. I'll use a couple of bungee balls to keep it rolled tight while traveling.
If it works, i'll come up with a mount set up like this for the poles.