I know that triple towing is illegal in some states. However, there is a trailer in which there is debate about whether it is a trailer at all. This is a swivel wheel trailer. Some consider this as simply an extension of the camper itself, rather than a separate trailer. This trailer allows back up of a triple tow without jackknifing. Almost all of the weight could be placed on the wheels and little on the tongue. I would not carry a boat or anything long on such a trailer. But if a swivel wheel trailer were made short, it could carry a lot of gear including something like a small motorcycle or generator while adding little weight to the rear of the camper. (If weight was distributed properly.) It could be a problem solver for carrying extra gear.
These can be bought ready made or you can build your own. I plan to build my own to be only 2 or 3 feet long behind my trailmanor. You can read more about it at:
http://www.doublehitch.com/