Regarding some previous posts:
Dealers are notorious for not setting up the WDH correctly. My dealer techs stepped back, and said "that looks about right", and sent me off on the highway. Their setup only replaced 60 lbs. of the "lost" 300 lbs. back to the front axle.
If you get the most of the lost weight back on the front axle, then the rear fender measurements should be less than without a trailer. Many trucks with high rear ends settle down nicely to almost level with a properly adjusted WDH, with no air bags, timbrens, or over load springs needed. The rear end of trucks are made to carry some weight.....but not too much weight.....that is why you have rear axle weight ratings. A properly setup WDH should keep both the front and rear axles within the weight ratings. If not, then you might need a bigger truck.
Chap , DW Joy, and Fur Baby Sango
2006 Ford F150 Super Cab 4x4
2008 Surveyor 263