another pic of swivel

taken wrote:
The definition of a second trailer is one that can freely pivot from side to side though it's hitching point. Since a swivel wheel can only pivot up and down and not side to side, it's not a second trailer.

Again, that depends on the particular state's DOT regulations. Some say that the trailer has to be permanently mounted to be considered other than another trailer. Do not rely on internet wisdom to defend you against a ticket if you are given one. Check with the DMV beforehand and be sure.

FWIW I towed a Smart Trailer behind my Big Sky so I am aware of the vagaries of DOT regulations for my state. It does tend to confuse the LEO's so the likelihood of you being stopped are not to high, at least that is my experience. I traveled through and stayed in some states that don't allow double towing and was never stopped. But just because I wasn't doesn't mean you won't.