Not to rain on the parade, but I think that a full size travel trailer might be a bit tough with the 2.8L. The 4000 lbs is not the issue, its the aero drag that gets you, especially if you start poking around in Utah, WY, ID, etc where you can be at high elevation with crazy winds.
I don't say this in a mean way. Just that I tow a 4200 lb dry weight trailer with my 2014 F150 Ecoboost that is tuned, making 500+ ft-lbs of torque and high 300's HP at elevation, and I have been in conditions that tested its limits out in Wyoming and southern UT. You get into a 30mph headwind and that 2.8L is gunna be giving you everything it has just to maintain 65-70mph on flat ground. And from my experience towing the past 4 years, you can't swing a dead cat without hitting some kind of headwind.
I do have some experience with tuning the 2.8L as well as its older brother, the 2.8L in the Liberty CRD. They don't maintain spec'd power at elevation. They will start cutting boost, and eventually fueling at elevations >6500', to prevent overspeeding the turbo and therefore running excessively rich.
I guess my point is, choose your trailer wisely. You will want something fairly aerodynamic. There are a lot of trailers now that are 7' wide instead of the normal 8' and then of course the tear drop shaped trailers.