Grand design and towing with a Ford Expidition

Weight-wise, you'll be generally in good shape. I do like the long wheelbase of the Max, but even the regular version tows well. As mentioned, you could have payload challenges if you need to carry a full passenger load while towing.

As for the hitch, I'd try it without the Hensley first. You probably don't need it. Grand Designs don't seem to generate many towing complaints, and the Expedition is stable as well.