I bought a set of Rock Tamers. THey are very nice. They do a good job protecting the trailers I haul - mine and the ones I deliver to Dealers.
I took them off Thursday night because I wanted to see if they were the cause of my lower MPGs... low and behold, after running two trips without them, I've concluded they WERE the cause.
They make 2.5 mpg hit running empty, and about a 2mpg running with a trailer.
Sounds odd, but it's true.
This is with them on my 06.
On my dually with AF811 camper, they probably won't affect the MPG since the truck is running heavy and has bad MPG anyway.