i was in your shoes back in 2015 looking for a trailer to tow behind my 2014 Expedition. I think you may be confused as to what your Espy can tow. I think I am maxed out with my 24 ft Jayco Jay Flight. My weight of my trailer is about 6000 lbs when loaded for a trip and my Expy weighs 6220 lbs with a full tank of gas and me. Also, my tongue weight is about 800 lbs. Now add your passengers and all the gear your Expedition will carry and you are very close to your 15,ooo lb. And I think your tongue weight will surprise you when you are loaded up.
I've seen Expy's towing some bigger trailers than mine but I wouldn't want to risk it. In 3 years we've taken many long trips in the Rocky's and my setup works very well. My only complaint is the gas mileage which ranges between 7 & 12 MPG depending on the wind and the hills. Hope that helps you
