The maximum trailer rating number of 11k+ are for a flat bed with 10% on the tongue. When pulling a travel trailer you will be running up to 15% (I run at 13-13.5%) on the tongue. You will likely exceed the rating on the hitch if you go north of 9k. So, if you are running a loaded trailer at 7800 you need to good suspension and tires.
Like mentioned in multiple posts I would order an F150 with the Heavy Duty Payload package. That will get you a stiffer suspension and LT tires. I tow an 8000 lb trailer (loaded) and my 2012 HD F150 handles it well with a good Reese hitch. My 2012 weighs 500+ more than the new aluminum trucks but there are multiple people on this forum towing in the range of 8k with the newer F150 Max Payload and are happy with the results. As for MPG I get 20 going 60 on the flat in 60 degrees. In town I have a lot of stop and go and get 15ish. If I am good on the lights on the outer parts of town maybe 17ish but no more. The HDPP has the 3.73 rear end.
The EcoBoost tows great - love the low end torque and how it holds power at elevation. Engine braking is weak but the integrated trailer brake control is very good..
If you think you are going to go heavier than 8k in a loaded trailer one day just go to the F250/2500 series now.
Good luck,
Stu