Don't discount the opportunity to demo a bike in your size. While it's true that small and extra-small demos are less common, they're still sometimes available. My friend was able to demo a Niner Air 9 (not sure if it was alloy or carbon) in XS when the demo truck rolled through last summer. Never hurts to check.... I would also check with your local dealer. They may have your size available, or know of a customer who owns that size and would let you try it out.

Good luck!