Securing the Underbelly

All the above. Tape, sheet metal screws, silicone. The material is called corrugated plastic. Made just like cardboard, but plastic instead of paper...

A tip I found online was to use cinch straps hooked every few feet so they support the rather flimsy material. This was after I struggled for an hour on a very hot day when I had to take mine off to repair a slide actuator.

Get the under panel (plastic) at a sign shop... in Tucson it was $20 for a 4X8 sheet. I created access points in the plastic to get to Drain valves and electric that were covered before.

Ours when we bought our rv had been taken down and apart for some repair. We put it back up with the screws and taped the seams and open areas with Eternabond. Yes it was expensive but it has held well and the plastic board underbelly has few things that will stick well. Be sure you clean the underbelly well before tying to stick anything to it.