We are 40' and tow a 26' trailer. Been all over the western U.S. and up into Alberta and British Columbia a couple of times. I would say close to 50-60k miles towing the trailer and we have been overlength with two of our three motorhome/trailer combinations. No issues here around 72' end to end, 69' with the last coach. The only issues I have run across is campsites are kind of hard to find unless planning ahead and making reservations. We don't "wing it" when traveling with the trailer. We camp with a group of guys from California at the sand dunes in St. Anthony, Idaho each July and they have some huge rigs. The smallest rig is a 40' Alpine coach towing a 26' enclosed trailer, the largest two are a 45' Newell and a 45' Prevost both towing stacker trailers, one a 30' Progressive and one a 28' Haulmark. There is one guy in their group who mentioned about two years ago that he was stopped and ticketed because he got off the main interstate onto a two lane road to visit some relatives. The CHP made him drop his trailer and he had to have it hauled to the state line where he was able to hook back up in Nevada and continue onward. He didn't know how much the fine was at the time but he did mention that the road he was on was also limited to a 40' coach so they nailed him for his 45 footer as well. All in all that is the ONLY situation I have heard of first hand who has had an issue. I follow this pretty close also because when I was drag racing we seemed to always be discussing this with other racers.
On a side note, I think you will be hard pressed to fit three Harleys and a Jeep wrangler in a 24' box. I couldn't fit that in mine. Ours has a workbench in the front so in essence the usable space for cargo is roughly 24'. We can haul our 04 Ultra Classic and our 2011 Jeep Wrangler Unlimited and it is tight. We were able to haul my son's Buell, our 2010 Dyna Wide Glide and the Jeep up until this year when our son sold his Buell and bought his Street Bob. Now we cannot fit both Dynas and the Jeep. To haul three Harleys and a Jeep I think you will be looking at going to at least a 28' box with no workbench in the front to take up space. I would mark out the box size with sidewalk chalk in your driveway or other flat area and then try to park the bikes and Jeep in the confines of those lines. Keep in mind not to break the plane of the lines when moving them around as you will have walls to deal with in the actual trailer.
Mike.
