Thanks All: good information. I've measured the front of the tow before hookup, and aimed for close to that measurement when WDH is attached. Have enjoyed good towing over lots of miles- but there does seem to be a lot of stress exerted on the hitch receiver. I keep watching for signs that the receiver may be twisting upwards- and have it inspected during regular service. My experience is that three links hanging rides very well- but I would be unable to set up without the cheater bar. With two links hanging, there is barely any tension on the chains, and the ride suffers.
I will remeasure using suggestions here.