I used to tow a 96 jayco designer and I was having the same problem. I was more concerned about towing level than i was about bridges. The back of my truck sat high and made my fifth wheel ride high in the front plus I was pretty marginal on bed clearance. Raising the hitch made things worse for level towing. I decided to put 3 inch lowering shackles on the trucks rear suspension. It was cheap and easy to do. The camper still rode slightly high but was much better than before. The only drawback is the leaf springs rides real close to the helper springs so I hear some squeaking when I drive real slow empty. Once I get on the road I hear nothing. A minor annoyance if anything.
