What I would recommend ....
Call the DOT of the state(s) you're going to be driving in and ask. The laws for RV's in each state are varied and across the board.
For Idaho (where I am) you're exempt from weight when pulling an RV, and can pull an RV with regular car plates. The kicker is you can pull doubles (RV plus a boat and trailer, or ATV/UTV and trailer. However, if you pull only a trailer they enforce the GCWR, which in my mind is dangerous and stupid.
I have what we call "T" plates, which are the Idaho plate/tag with a "T" as the last character. I'm registered for 14 thousand pounds, which I believe is the minimum.
-Kris
