I dont thinh the unbalanced wheels have much to do with the sagging. It hasa lot to do with a very flimsy frame I was supprised when I pulled the belly pan on my 65 tradewind as to how much under built it is much of the satrength of the airstream has to do with the way the superstructur is built.But the weight behind the axels is excessive when the holding tanks are full. )One should always try to dump before driving if at all possable. 1/2 to 3/4 full is eaven worse as the pounding thats takes place in an unbaffeled tank can be destructive.far worse than the full tank would be. I have a total of 45 gal capicity in my gray and black water tank. I try never to go any distance without dumping .Also full tanks tend to throw the trailer out of balance.
Jim Smith
1965 Tradewind(The Silver Abaltross)
1992Dodge Cummins Diesel