I have to say that in my opinion, the most uncomfortable time on my Wing is anything under 5 mph, especially two up. I call my bike "Orca" the whale simply because of it's mass which is always a challenge at slow speeds and I'm 5'10" and 210 pounds. That being said, I can't imagine what it must be like to control that rig even with trailer brakes. It's kind of neat but really I just don't get it. Why adapt a motorcycle to do the work of what a truck should be doing? It is an eye catcher but if I had a nice car that was broken down on the highway, the last thing I would want towing it is a motorcycle!
The theory behind it is that it can lane split or run the shoulder and get to the broke down car much more quickly than a tow truck. They get the car out of the way to let traffic get moving again.
I can't imagine doing that with stock gears either, it has to have a really low speed rear end. A good set of surge brakes on the unit so you have compensation for varying loads, and only use it to get to the next exit and it seems like it has some usefulness.