Towing a TT

It goes without saying that the closer a towing combo is to being maxed out the less desirable the towing experience. Towing comfort while underway is different from one driver to another. Some have no qualms pushing the limit and are plenty happy with their results, after all they got to where they were going. Others go to the opposite extreme to have that feeling as if they weren't towing at all, their choice, their money.

Todays half-tons offer some pretty impressive towing specs properly equipped and there are plenty of RV manufacturers pumping out lightweight rigs that in-themselves are pretty impressive with all their amenities. If you go with a 3/4 ton you will be able to tow pretty much any TT available, many of the heavier high-end TTs have the same floorplan as their 5er counterparts on a single level deck, although storage isn't as expansive.

We have a Chevy 3/4 ton gasser with 4.10s to haul our 33' 10K# TT around the four corner states, nearly all of our RVing is above 5K' elevation where a gas engine's power is derated 3% every 1K' of elevation. IF you decide on a gasser don't be afraid to let her rev up as they are designed to do just that in order to reach their power band. Going up the many inclines in our region, our gasser happily roars into life to carry our rig where it needs to go.

The manufacturer already put in a safety margin.

If you want to pull a popup with a 1 ton dually diesel, you can. You can cruise up steep grades without downshifting and it won't even feel like you have anything back there. Of course it's overkill.

Anything below 100% should be fine (assumes all ratings are below 100% not just the towing number).

Put more attention into PAYLOAD rather than tow rating.

As everyone will chime in, most of the time your payload will be maxed before your tow rating. I'm between 90-95% of my tow rating, and the truck is working hard.
I've got an older GM 6.0 gasser with the 4spd tranny, and on the highway at 65mph, I'm normally in 3rd gear turning 3000 rpm. If it is really flat, it will hold the speed in 4th, but any incline and it is back to 3rd. In the mountains of North GA, and East TN, I've had a couple of hills that I got down to 1st gear, turning 4500rpm, and it would not hold the speed in 2nd gear. It does the job, but I feel I'm working it to hard sometimes. The next truck will have a higher tow capacity.

I would also like to stay at 80~85% but it isn't a stead-fast rule. A vehicle is fine right up to it's max rating but it's been my experience that it isn't a very enjoyable towing experience like that.

I wouldn't go above 85% wet/loaded.