Well folks, here's what I've learned.
My 2008 Nissan Xterra has a GVWR of 5400 lbs. and a GCWR of 9658 lbs.
I weighed it this morning loaded as it would be if I were towing a travel trailer (full gas tank, all my photo gear in the back, spare tire, tools, and 1 passenger (me), and it tipped the scale at 4830 lbs. I calculate that as meaning it could handle a hitch weight of up to 570 lbs although the Xterra is only rated by Nissan for 500 lbs.
The good news is I've been looking at a 24 foot Keystone Passport Ultralight (Mod. 195RB) and, fully loaded, it would top out at 5200 lbs. However, since I will be traveling alone I can't imagine adding more than 500 lbs of cargo just for me. That would make the TT's loaded weight at around 4211 lbs.
The big question mark now is the Xterra's trailer frontal area is limited to no more than 60 sq. ft. The 195RB is either going to just make that or just miss it. So far, I haven't been able to pin down that statistic. Guess I'll have to take a tape measure to a dealer and check it for myself.
Now, have I miscalculated any of the above or overlooked anything I ought to have considered?