We used Scotch Permanent Exterior Tape to attach 2 flexible
Solar Panels to the roofs of two Scamps about a decade ago. Our
Scamp 16 has had one taped to the roof and has been in all kinds of weather on all kinds of roads without a single issue.
The advantages are no mounting holes, low
weight just a couple of pounds, low air resistance, the panels are less than a 1/4 inch thick, and no one except you knows they are there.
The tape is also good for attaching other things in the
Scamp. We have a few plastic trays that are held to the Scamp's wall by this tape. $50 inches of the tape is only $15.
I have never noticed the heat loading inside the trailer.
https://www.amazon.com/Scotch-Perman...1478356&sr=8-5