You mention a TT or 5'er, so I assume that means you already have an offroad capable pickup truck?
If not, FWIW there is a completely offroad capable "Class C" RV similar to a TC but with a lower CG (because it's built right onto the main frame) than either a TC or an Earthroamer - and it's much less money than an Earthroamer. It can be ordered built on just about any pickup truck frame to start with, which of course means that the truck that the builder starts with can have just about any traction, ground clearance, and tire setup you could want.
Here's a link:
http://www.deesrv.com/pages/overlandvehicle.htm