On another board I'm DoubleTow
Back when I had a real job and weekends/holidays off, towed my 26 ft 5er and 26 ft toonboat/trailer bout every weenend and for vacations. Colorado mostly, but been to Powell. I've seen many pulling two "tag" trailers, never done it myself. Since commercial most haulers I see have a 5th wheel or GN, then a "tag" hooked to that. Myself, I really don't know what the differences would be. Like I said, seen it, never done it. Generally rear trailer needs brakes > than 3,000 lbs, and it's own breakaway, and 70 ft max overall. I'm not all that thrilled at backing even a single trailer, don't care what kind. Last spotter I had was watching the birds, let me back somebodies 5er ladder into a tree. I sort of ask him what he thought he was there for, cept to keep me from backing into something he could see that I couldn't. . . really didn't have a good answer. Far as I'm concerned, less backing the better.
Cheers,
Steve J.