We use two Expeditions and would love to have a new one as we tow in the same mountains the test was run. That said I wouldn't go over 5500 pounds dry weight to keep the tongue weight under the limits.
Payload is different depending on the truck and features. The more features, the less payload. This is where the Expy may do better than the Navigator simply because you can get fewer features. Our 07 has a 1745 pound payload and I have seen higher.
I hoping in a few years I can find a nice low mile 15 Expy coming off of a lease to snag up. Ours are in too good of shape to justify buying a new one now.
