Sir,
One thing to consider is the safety aspect of what you are wanting to do. Legality is a must but, you need to keep everything else safe too. The anti sway bar is a good idea on the second trailer but, you should also consider the brakes on the trailers and on your rig. Make sure that all are up to par and you may also need to make special porvisions for a second trailer plug. You will want all the lights working as you will be quite long. For the Moab Easter Jeep Safari in 2007 I pulled double trailers from my home in Los Alamos, New Mexico to Moab UT and back. No issues but, I was using a tandem dual, back hoe trailer and then my tent trailer behind that. The tandem dual has eight tires on it and the tent trailer only had the two. I could not tell the difference between pulling the back hoe trailer with or with out the tent trailer behind it. I was just a tick over 69 feet in length but no body called me on it. The back hoe trailer has brakes on both axles so I just turned up the electric brake contorler a little to adjust for the added tent trailer. Also, you will need to make sure that you are not going to be backing up very far. Every place you go you will need to plan ahead and make sure that you can just pull though. I only had one problem and that was when I turned sharp. The tent trailer started to make contact with the back hoe trailer.
LT.