Don't know for the three sled. But to give you an Idea i have 14 foot With 5' v. And it will haul two full mountain sleds. They are tight but they do both fit. Both face forward also.
Do what I should of done. Draw out the size you think you need and try to set the sleds in that box. If you cannot the awnser will be clear. Is there enough room for what you want? When I went enclosed I noticed one thing. I carry more stuff. All oil is in the trailer,spare parts, folding chairs to sit down on. "For getting dressed"
I pulll my trailer with chevy 1500. With the 6.0 and six speed auto. It pulls somewhat tougher than a open two place. But it definetly gets the job done well until the 50mph head wind.
Extra two cents put all doors on drivers side. Driver can see better for filling sleds on that side. For me around home, pull up to barrel fill pickup pull ahead 15 feet fill sled. My opinion if I were to do it agin and order a trailer. I would forget the gas door and just put in another walkin. On a trip bags are always close to the doors if you need something