There seems to be as many methods of protecting the insides of wheel wells from rocks as there builds. My concern is that with the sticky tires that I'm using, I will likely be throwing some rocks at the inside of the fiberglass with considerable force. Just as an added protection from "stars" in the paint made by those flying rocks (over the usual bed liner), I have added some closed-cell foam.
I used black neoprene yoga mat material from Wal-Mart and 3M General Trim Adhesive (Part No. 08088) that is heat and moisture resistant. I will follow-up with some bedliner for the rest of the wheel wells, particularly in the area around the front at and below the headlamps.
After trimming to fit, I cleaned the material well with preps-all (grease and oil remover) and a thorough bath with hot water and Dawn dishwasher detergent. Once they were dry, the side that was being glued to the body received a scuffing with 80 grit sand paper to take the top, shiny layer of rubber off. I applied two coats of the adhesive to the mats and the body and pressed them in place using a roller once they had tacked-up.
Here are a couple of photos:
Rear:
Front: