What does your manual say about length restrictions? Don't look. It says NOTHING about length. Only about weight. Stay inside your weight capacities, and you are good to go. You will run out of weight LONG before you run out of length.
But do remember. The longer the TT, The harder it is to find a place to park it. You will also need to swing out farther when turning, and wait longer to clear traffic when changing lanes. But that is pretty much the downside of it all. They are no harder to tow.
If you set it up correctly. It will follow you like a good dog, and every time you look in the mirror. There is it.
