We didn't do anything special. I used 4 hollow wall anchors similar to these to hold the fan to the plywood:
Crown Bolt #6-32 x 1 in. Zinc-Plated Hollow Wall Anchor with Truss-Head Combo Drive Screw (5-Pack)-00469 - The Home Depot
I' didn't read the specs for these, but the ones we purchased were for 1/8" plywood.
The fan was installed early in 2006 in preparation for our trip to Alaska in 2007. At the time we had about 40,000 miles on the coach. We traded it off in 2013 with about 110,000 miles on it. The fan never had any problems and worked great when we traded in the coach.
We used this fan:
https://www.campingworld.com/includes...h%20Remote.pdf
At the time we bought it from PPL Motorhomes, but they no longer carry it. The fan was ultra quiet and vibration free.
