Don't do it, not only is a double tow illegal in many states, you would certainly be over the maximum legal length in most states, and very dangerous to yourself and others on the highway. It's also quite likely you will be exceeding your GCVWR with that much in tow.
I found something called a Duece Trailer that I can put my atv's on as well and my toad. They look pretty good, little expensive for me right now so will have to wait for a day or three. Anyone use them? Can tell me how they like them?
Years ago I pulled a travel trailer with an ATV trailer behind it using a crew cab pickup. It was a pain in the rear because you couldn't back it up more than a few feet. As was mentioned it is an illegal combination in most states which was clearly explained to me by one of Burns Oregon's finest. I don't know anything about the trailer you're looking at but currently I have a 40' MH and a 24' trailer in which I can haul two Motorcycles and a Jeep Wrangler. This combination seems to be pretty good all things considered.
I just went through a similar exercise as you. I have a motorcycle I want to take with me along with my toad, which was a Grand Vitara. My current bike only weighs 350lbs but putting it on the back of my coach with a 70lb ramp would add 650lbs to the rear axle. I only have 600lbs left right now. Once I realized I most likely would be getting a slightly larger bike, weighing around 570lbs, the ramp on the coach was out. Knowing triple towing is not legal anywhere in the east where we spend most of our time I traded the GV for a Dakota pickup. Now I can take both toys and still be legal. There is a guy here at TGO that carries two ATVs on his pickup. He loads them from the side with a ramp. Guess it places them awfully high but he's done OK so far.
Thanks for that information. Ditch digger have you ever gone thru any of the states like california where they say "no" over 55 feet or any that say no over 60 feet? I am just wondering whether that will be a problems or just an irritation? In other words do they stop you and ticket or do they stop and just give ya a warning? There are 20 states the say 55 or 60 foot max.
I think we are going to trade in our tow dolly and our atv trailer and pick up an enclosed haulmark trailer that will carry both the car and the atv's. I am thinking that a 20 footer might do the trick but will talk to them to be sure.