I think mine is a full size... I'll have to look again.
Anyway, what all these guys said. The ONLY reason you wouldn't want to run a spare on the rear for RWD is if you're running a LSD (limited Slip Differential). The difference in size has the potential to destroy your LSD. But, for safety sake you still are pretty much forced to run it on the rear. What's all this confusing BS amount to? For RWD (applies to all, but especially important for LSD equipped)... Put your spare on the rear when not full size, but find a new tire ASAP (we're not talking 200 miles later here...).