That looks really good. I like the idea of a raised platform for the tent. No flooding, insulated from lightening stikes, quite a bit more critter proof, and so on.
A couple questions...
(1) how does it mount to the roof? In stock locations?
(2) what is the load capacity of the Xterra's roof and how did you arrive at the figure?
(3) With the mounting points you have, how well is the load distributed?