Due to the differences in light fixtures, a one size fits all solution may not be possible.
Here's what I did.
My fixtures had a white reflector/heat shield that sort of bowed out from the under lying plastic. This made it impossible fotr the LED panels to lay flat and for the tape to have any chance of holding.
I removed the reflector/shield as it really isn't needed with LEDS.
At 12 volts they run much cooler than the incandescent bulbs they are replacing.
I was then able to stick the panels on the flat plastic surface that was underneath.
The tape isn't real 3M. I wasn't confident in it, so I put a dab of silicone (because I had a open tube handy) on each corner.
Been on quite a few trips an miles of rough roads. Not one has fallen.
I did have one out of about 20 that had a failed solder joint. It was easy to resolder it. Even it I had replaced it, at the low cost, I wouldn't have minded.
One thing to keep in mind. Although the panels run cooler than regular bulbs at 12 volts, at higher voltages they can get hot.
So there is potential for over heating when on shore/generator power.
To prevent this I installed voltage regulators on the two circuits that I have LEDS on. Cheap enough and not too hard to do.