[RamItOne]

Just read about the trailer, the guard dog won't work.
What you can try is tilting the 4wheeler, ie block the front of the bed with lumber about 1-2 feet high, roll the front tires up onto it, that'll reduce the space it'll take up. Not great but it could work.

I seem to remember someone on a dodge site that had two stacked sideways on top of the bed. Don't remember the structural setup though.