I appreciate all this information :-)  But what we really want is a "tent".  A warmer, more solid, faster setup, "tent".  Since so much of our traveling is during the winter, plumbing is kind of a moot point.  Heat can be supplied by an electric heater, plugged in at the RV parks we tend to utilize.  I HAVE camped quite nicely in an E-150 cargo van... but since we have the truck anyway - a TC makes more sense than adding another motorized vehicle to the mix.
If I lived closer (and knew that we'd use it often enough to justify buying one new) - I'd trot over to Four Wheel, and have them build me a shell.  But those are hard to find used..... so I'll keep searching around here.  The one I had my eyes on got sold yesterday before we could look at it :-(