One of our solar panels is semi flexible and mounted on the cabin top. Whilst it is claimed to be "walk on" we don't because although the panel will bend about 3cm per metre this is only in one direction and the cabin roof under the panel is convex so curves in two directions. the result is an air gap under the middle of the panel of about 3/8". Nylon washers used to mount it ensure there is a little movement so it can flex and the dog Angus at 40kgs likes to sit on the panel because its warm
The panel is dimpled so good none slip surface, however there are lots of complaints on the net for these panel stopping working in just a few years rather than the 25 year panel life they seem to claim. Given the very high cost compared to a rigid panel I don't think I would buy another one now. Output is at best 1.4 AH from a 45w panel, not great and that is when it isn't shaded. Our 80w rigid panel cost 1/5th and produces 4x the AH.