I'd agree that a 16 would be good size. That's what I was told the trailer we got to haul ours on was. Then we went to load up the XJ and realized we were a little shorter, about 4 feet shorter. Turned out to be a 12 footer, with a fixed headboard at that. It does fit, but with the front bumper against the headboard you've got maybe 6-8" behind the rear wheels and the rear bumper actually overhangs the back of the trailer. Luckily it's pretty well balanced like that but it would depend on the placement of the trailer axles. So yeah, I think a 16 would be ideal, but you can make do with a shorter one as long as it's properly balanced for the application. I'll snap some pics next time she's loaded up, you can see there's no room for adjusting the weight distribution. Unfortuneately I've gotta keep looking for a trailer since squeezing the MJ on there would be a real chore. The old man's beat up ol' 16 looks better everyday even if it does need a frame up rebuild.