Am I correct that 303 is best stuff on rubber and gives a satin result on tires? I don't like real shiny tires. Vinylex is hard to find locally. The 303 website says that 303 is the best stuff on fiberglass and but wax is not. I just put 2 coats of wax on my bed cap and now I am confused.

 

I would stick with wax on the fiberglass. It will last longer. You could always give it a shot of 303 for extra UV protection. I would even consider a marine grade polish some have Teflon in them and they work great on my boat