Ha! Plywood fenders would be interesting...
I'm thinking about doing something different on the outside lip of the fenders. Instead of using that almost 2" tall piece of angle, what about a 3/4"-1" pipe? Easy enough to bend and strong enough to give the fenders some extra support...
The front flap would end at the bottom of the trailer frame, the bend in the pipe would give me a rounded corner on the front. The rear is going to have a 12" platform level with the top of the trailer frame. One side will eventually hold the propane tank for the kitchen, the other will likely eventually hold a gas can or 2.
MS Paint demonstration of the pipe... it would be under the diamondplate.