I've used two different single wheeled trailers. A BOB and a home built. If you're going to encounter any sort of logging trail or other single track trail, they are the way to go. If you're only going to see improved trails that would work for a two wheeled trailer my first inclination is to go for some overbuilt wheels and conventional panniers and racks.
__________________
Birth Certificate, Passport, Marriage License Driver's License and Residency Permit all say I'm a Fred. I guess there's no denying it.