More specifically, you can't put the tongue weight of a TRAVEL TRAILER which is usually 12 to 15 percent plus you and your gear and haul it. There is a HUGE difference between a travel trailer and something like a boat trailer, a distinction neither the manufacture nor the RV salesman will make.
Most boat trailers have around 10 percent tongue weight. They are low profile and sleek with low aerodynamic drag so they are stable at 10 percent. The maximum hitch weight for Expedition is 920lbs. Notice how this is 10 percent of 9200lbs? My 07 Expedition EL has a similar maximum cargo capacity at 1672lbs. I could load up my family of 5 plus a cooler and beach toys and have 920lbs left available for tongue weight. Hook up a 9000lb boat and head for the river, and I will be within all limits! Ever notice what almost all SUVs are towing in their ads? Almost always big boats!
Now lets look at TT. My family of 5 and cooler still weighs 600lbs so I still have 920lbs available for tongue weight, and it would be the same if it was just me in the Expedition, the tongue weight is limited by the receiver. TT mostly have a huge flat front with massive aerodynamic drag. You are towing a barn door. At 10 percent tongue weight, the drag pushes back on the trailer so hard it can induce sway and become unstable, this is why travel trailers are 12-15 percent. Lets use 14 percent
920 / 0.14 = 6571lbs.
This is loaded ready to go camping. Since "dry" weight never includes anything lets start subtracting. We dry camp so we always have a full fresh tank of water, Ill look at my trailer add ons
Water 56 x 8.3= 464lbs
Propane 4.3 x 15 = 64.5
Batteries 2 x 65lbs = 130
Spare tire = 40
Leveling jacks = 40
TV/video = 10
So I have 750lbs before even adding food pots clothes etc. So even if you have smaller tanks than me, it is easy for a family of 4 or 5 to add 1000lbs over the dry weight of a trailer. So if you take that 1000lbs off the 6571 you are looking at trailers with dry weights of around 5500lbs.
This is why many of us use 5500 to 6000lbs dry as a general rule of thumb with a couple exceptions when talking about any half ton SUV or truck, and actually many half tons have less or much less payload than the Expy which further limits options.
Of your choices the Aerolite 242 is the best one, the 250 is pushing the limits. Anything more and you are first going to exceed the receiver limit of 920lbs followed shortly by the rear axle limit shortly followed by the payload limit.
I am so glad you are taking what the salesman tells you with a grain of salt and doing your research first. I am a Mechanical Engineer and have run numbers many times using my Expy and different trailers as well as played with other tow vehicle numbers. PM me if you have any questions. Good luck to you and stay safe!
