Just purchased a 2016 dodge ram 3500 with the trailer prep package and auto leveling system. Because of the prep package I ordered a Curt 20k hitch that is designed for the unit. I tow a 2014 Big Country 3650RL. My question is, the hitch has four height settings, to accomplish the 4 to 6inch clearance over the bed of the truck, do any of you have a recommenced starting point on what hole to use?