I also have an unusual trailer set up. The trailer I aquired was a boat trailer which had been converted to a utility trailer. Since my boat has a flat bottom, I wanted to keep both aspects. The bunks are side to side and held on by wingnuts. Then I manufactured a roller on the rear of the trailer with scrap pieces I had laying around. This is as of yet untried - so let me know if you think it will work - or not.
Don't know if these images will show up - if not, you can see them here:
http://gallery.bateau2.comdisplayimage. ... at=1&pos=0
Hoping for Mothers Day launch - Ross