“Comfortable” is sort of an elusive word, it can mean many things to many people. I have an F150 5.4 4x4 with a 3:55 axle. Most of my travel is in the mountains and I wouldn’t be comfortable pulling a 6000# TT. Mostly because I don’t have much tolerance for slow, high rpm climbs. Others would be very comfortable with that weight and even more. You do have the 6 speed transmission which I don’t have and I don’t know how much difference that would make.
In the flats the heavier TT is comfortable to tow. But you will certainly notice the weight if you do much mountain driving and only you can judge whether you would be comfortable with it. In general, though, if you do a lot of mountain driving the lighter the TT the better. I’d avoid towing near your max unless you always stay in the flats. My perception reading posts for a long time is that most people who tow near max aren’t happy with it, the TV’s kick down a gear on the slightest grade.
I haven’t given you any numbers to work with and don’t know if this is much help to you. But I didn’t notice any comments about the terrain you plan to tow being a factor in your comfort level. Good luck.
