The lenth law for commercial trucks is 65' in most states I think, would have to get a truckers atlas to find it for sure. How would this mod void the frame warranty? I don't intend to modify the 405RW frame at all. The leveling jacks are bolted on. It's a one piece system that mounts by bolting to the rear bottom of the frame. A custom cross bar reciever would mount in it's place. And if rear leveling jacks were needed; yes bottle jacks would do; but may have a bleed down issue over time. I would use maybe a two ton jack stand, two each. But like I said before; I may never use a jack in the rear anyway; because I need to have the rear as low as posible to ease loading and unloading the bikes. I've been pondering the idea of trying to put three in that garage. Just looks too tight, and too close to get a good tie down. I use ride in stands also. They do take up a little more room. But the piece of mind knowing the bikes are secure, and so much easier to park in the stands. We have two full size Harleys, with bags. I've seen pictures of folks doing the double pull in the past. With a fifth wheel as the front trailer, theres not much of a stablility issue. The number two trailer shouldn't be so heavy as to need brakes, So no larger than a 12 to 16 footer is best I would think. Forget about backing up so plan way ahead so not to embarras your self. The hook up routine is art work.