What about factoring in the drop of the rear end when you add tongue weight? I like at least 500 lbs tongue weight so it tracks nicely so I let the rear squat maybe 2 inches. I run a solid cast iron hitch with at least a 10k 2-5/8s ball, its only a 4" drop and works just fine keeping my trailer fairly level. If you run a 6" drop, then add plenty of tongue weight I'll bet you the front of trailer will be lower than desired.