I ran a 34x9.5" swamper as a spare in the stock location for a few years w/o problems. It didn't hang down much lower than my Smittybilt bumper.
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When I built a new rear bumper I started carring a full size (35x12.5") spare inside, strapped vertically to the roll bar.

Now with 37's, I'm not sure what I'm going to do. Last trip I just laid it flat and strapped it down in the cargo area, but it really takes up a lot of space. I may build a rear carrier, but I don't really want to have that big thing hanging off the rear and loose the visibilty... <img src="/forums/images/graemlins/pfft.gif" alt="" />