[PGSigns]

What they look at on a hitch is the relationship of the ball to the hitch. The weight it will carry is based on the ball being close behind and even with the hitch. As you put the ball further back and down it changes the way the loads are transfered through the receiver. That is where the loads on the receiver change. If you look at drop hitches you well see as the drop increases so does the load rating. Just lots of factors on what loads and where the loads are seen by the truck than just purely the tongue and trailer weight. The adjustment of the weight distributing hitch and a stiffer set of shocks could make the change that you need.
Jimmy