So my swing out rear door is sagging and clunking when I open it...no doubt due to 9 years of carrying the weight of a spare tire (now a 235).  I'm considering buying an independent swing out spare tire carrier, but this will be an expensive solution.  Has anybody come up with a solid fix for this problem on aging swing-out doors?

The door is designed to take a 235 (stock on the GV is a 235/60-R16) - mine has had one hanging there for 13 years - no sag, no clunk - and you're the first person I've heard complain.

Interesting.  I've seen hinge reinforcement kits for jeeps, but nothing for our particular vehicles.

My back seat's folded down w/ a 31x10.50 spare there.  No passengers in the rear until I get a bumper w/ carrier fabbed. 

i never had an issue with a dor or heard of one either. i got a junked 2002 vitara witch the rear body is very bad but the door still works like a charm. must be worn in the hinges. id start by changing those first, other wise for relocating the spare its either a custom mount bumper thing, inside the trunk or on the roof of the truck. on the roof of the truck would be the cheapest and the best place to be out of the way. but not everybody loves that look lol

The only problem with my rear door is that it won't stay open. If I'm park even the tiniest bit facing downhill the door will slam shut the second you let go of it. Come to think of it, my drivers door does that too. 

That's an easy one to fix Dan - there should be a gas strut at the bottom of the rear door - it's either missing or dead - replace it.