I thought about doing this also. I was going to use a fixed tongue trailer so you could not jackknife it when backing up.
Anyway, I never did anymore with it. Still have about 9-11 months before I hit the road.
Here is a web site that talks to towing more than one trailer in various states.
for tamdem towing
2001 Supercruizer, Cat Power &16 RAM 3500 Laramie, Dually, Bed Tank, Air Hitch, Air Bags, In cab controller
2008 Carriage, Carriage. IS, Disc Brakes, Bigfoot, , Full Timer Since 2011, CTC 17771