We have the exact same trailer as Litespeed above. '99 36RLTSO Travel Supreme. We must have more crap in ours though. It weighed 16,800 last year when I weighed it. We are 25,500 rolling down the road.
We used to pull it with an auto SRW, and it was SCAREY. It always felt like the trailer was trying to push the rear end of the truck around on tight curves or sharp turns.
We traded for the dually in my sig, and while it is still a load for the truck, it feels much more stable. Now it feels like the truck is pulling the trailer around a curve, instead of the trailer pushing the truck. Tight curves such as an on-ramp were the worst. Now the trailer goes where I want it to go.
We travel mostly in the Western USA, and have not had any problems. I try to stay around 60 to 65 mph. I will back off even more in heavy traffic. On an open interstate, I will get close to 70 if I am "getting a run" at a hill. Usually I stay right around 60 though. That feels pretty comfortable.
If we were retired, we would be shopping for an HDT. I would by pass the MDT and go right to the HDT. But, due to work constraints, we still need to get into the occasional parking garage, or tight hospital parking lot. That can be a challenge enough with the dually.
Hope this helps your decision... ... . Steve