Not a 5er, but I used a Rock Guard for my TT for years. It DID help a lot. Mine had 2 sets of 2-3 inch flaps that over lapped each other, from the end to the middle. It attached over the hitch that slid in the receiver. I also had mudflaps on my truck. Between the 2, I feel pretty certain it's saved my campers from getting beat up.
Now, I have an Equal-i-zer WD hitch system. It doesn't fit right on hitch any more, so haven't used it in a couple years now. But, I very seldom, if ever, go down gravel roads.
They do help, I really believe that!