Some have. I’ve recently read that it’s not a great idea because they get overheated but I have no real world knowledge. My solar panels are mounted about and inch above the roof do they get airflow all around.
I installed 2 on the sloping part of my small RV in Europe. Very easy installation with Sikaflex glue, they weigh nothing ... Among other advantages: the wind does not take in.
I use this RV especially in winter, so the temperature is cooler than in summer. And especially, as the sun is rather low in this season, the inclination promotes maximum insolation ... provided to park the vehicle in front of the sun!
I went from 100 W to 340 W at a light cost; I took the opportunity to improve my system by changing the PWM controller for a MPPT of 40 A.
All in all a very effective system to feed my 2 x100 A flood batteries (which I intend to replace soon by a single LiFePO4 100 A) as I did here in Canada on my PM.
Advantages are a super easy install with no drilling and a more stealthy look.
The downsides are cost per watt is gonna be quite a bit higher. Most of the cheaper models seem to have a pretty subpar coating that does not last long. Cupping is another issue. Performance overall will probably not be quite as good as a standard panel.
I looked long and hard into flex panels. But the cost for the quality of product you are getting just isnt worth it to me.
Ill note that there are many people who install standard panels without drilling. Think theres even a van upfitter doing it now. 3m VHB tape is pretty strong stuff. Not sure if I have enough balls to do it though.
I have seen them on boat cabins and decks and people walk on them! They work great as dispersed panels too because they are lightweight and thin. They can be monocrystiline cells so I expect the output to be the same as glass covered panels. They are about 30% more cost than rigid panels but might save a bit of mounting costs. If I had a reason (like needing low profile) for them I wouldn’t hesitate. The cupping issue was noted a few years ago but may be solved you would have to check. The problem was with circular cells so I might consider this one: