A lot of sites recommend you put the ball on the tow vehicle higher than the coupler on the trailer.
I could never get this to work on my F150, I had to lower the ball by about 1 1/2 inches to get the trailer to sit level. It seems like they want the weight of the trailer to "push" down the ball and rear suspension.
Is this a function of trailer weight vs suspension of the tow vehicle as to how high the ball should be? Maybe the trailer did not weigh enough or the suspension was too stiff to properly align the tow vehicle and trailer?
2013 F150 Crewcab Ecoboost Max Tow
3.73 gears 157" wheelbase