My 2003 M8801 was similar to a stress skin panel made of 40 mil EPDM glued to 1/4 inch ply bonded to ~1 1/2 inch block foam with ~1/8 inch ply on the inside.
It was very strong.
The perimeter of the roof and the roof openings were 1 1/2 x 1 1/2 inch solid wood for fasteners.
There were 1 1/2 x 1 1/2 inch solid wood cross members spaces on 4' centers.
If the M2902 is made the same way, I think it is, the only thing you would worry about is drilling into wiring.
If it were me, I'd give customer service a call and ask for a diagram of the wiring just to make sure you don't drill in the wrong spot.
Other than that, the 5/8" well nuts should expand when tightened and hold it fine.
Joe and Evelyn