Hmmm, using the rear VX door as a full-size spare mounting point like on Tom's VX gives me the hebee-jebee's. It is way too much stress on the VX door hinges and thin sheet metal.
A much better idea is to use a 2" square receiver tow hitch for the "mounting point" for a full-size spare. Just go to www.JCWhitney.com and type-in "SPARE MOUNT" in the little search box. There you will find various 2" tow hitch mounts for spare tires.
Plus, you can use the full-size spare only when you go 4-Wheeling, and leave it off (at home) when you're around town. This method will save you from butchering your VX rear door; and save gas money, as you would only use the big spare tire when going off-road.
TRIATHLETE--- Your idea is the very best of all, and surely the cheapest; that is to merely strap down a full-size spare in the cargo area behind the rear seat. Be sure to use motorcycle straps thru the wheel and tied to the anchor loops in the rear cargo area to prevent the spare tire from hitting you upside the head in case of a roll-over accident. This method works well, as the full-size spare can just stay in the garage until it's needed for an off-road trip. Simple.
The baja style mount like Jolly Roger's (see below) "looks good"; but is really impractical, as it totally eats up too much valuable cargo space that could be used for other necessary off-road/camping gear. Total waste of space.