Assuming you don't have too much stuff and people in the Navigator L, you should be fine with a camper with gross weight 6500 lbs, with a WDH that's properly dialed in plus anti-sway.
Walaby wrote:
1) Lincoln Navigator L, 4WD, appears to have a wheel base of 131". If I recall, 119" wheel base would accommodate a 20ft TT. Every 4" additional wheel base would increase TT length by 1ft. That seems to be the generally accepted formula. So, 131 - 119 = 12 inches additional wheelbase, which would accommodate 3 additional ft of trailer. Puts you at around 23 ft. A few feet short of your Airstream 27'. You have to decide how much you buy into that formula.
I agree that wheelbase is important for stability. However, I've seen that formula floated around quite often, and it's an ok guesstimate to start with, but it's really not quite accurate and I wouldn't put too much trust in it.... I have a 112" wheelbase TV that tows a 24' camper just fine--no sway, no issues whatsoever in 3 years of towing this camper (Of course, I feel that I may be at my limit and wouldn't go to a 27' TT).... Also, by that formula, a F350 with a 137" wheelbase would mathematically only be able to tow a 24.5' camper--we know that doesn't happen. :)
