I have wondered if anyone, parked long term has constructed a light frame that covers most of the roof area and about 6 or 8 inches from the air conditioners skylights etc.
Not sure schedule 80 3/4 pvc would not warp from heat but several little standoffs along the length might work. Some aluminum sheet secured with ties, after sizing to frame would reflect a lot of heat through the roof, much like a mini poll building. Secure it with bungees or something. Then again with winds maybe not such a good ideas unless a lot of refinement.
perhaps someone has ideas that are more practical for transport apperrcne etc.
thing that would make the most sense is ordering RVs with cold weather package, meaning a lot more insulation. If it can keep out the cold it can keep out the heat.
I noticed in Big Bend area some RVs parked for a long time went with a semi pole barn roof with porch area covered too. Brain dead now for better description. It could be tastefully done.
A thousand dollars for the summer or less?