Have you thought about using a drop receiver? Blue Ox makes several types including an adjustable one rated at 10,000 towing wt. and 1000 tongue wt. Between the drop receiver and the Hensley drop hitch, you shold be able to get the right height. Here's a link to the information...
Blue Ox Drop Receivers
It looks like you can pick one up for about $200. Google the part number BX88223 and you get lots of hits.