Oasis RV in Tucson keeps rising to the top.
Recent discussion on this topic is at
http://www.airforums.com/forums/f206...est-42761.html. What direction are you headed next?
You'll certainly face a variety of wait times before they can do the service. I'd still base my decision on quality and reputation.
Protect the dump pipes? They do have to be down that low to drain your tanks. Not sure what else has been tried. Likewise people have had their wheelwells shredded when they had a trailer tire blowout.
Best wishes and please let us know how it turns out.