wing_zealot wrote:
It doesn't matter if the rear end sags.
It might...the trailer AND the truck are supposed to be level, and the OP hasn't given us enough info to determine what they mean by "sag".
Most trucks are designed with a forward rake, so that when unloaded the rear sits higher than the front, and when loaded the truck sits level. If that is what the OP is calling "sag" then it's fine and normal. However, if when loaded the rear of the truck sits lower than the front, that is NOT OK and means that the headlights will be scanning the trees for birds when driving at night.
The weight distributing (WD) hitch should be adjusted so that both the truck and trailer lit level, unless the trailer is beyond the ratings of either the hitch or the truck.