I am also a smaller rider 5'4ish/110lbs. During the course of regular riding or even aggresive racing, there is not much I can do that can stress the frame to anywhere near the levels it was tested at in the factory.

I would not get too bogged down with frame material choices at this point. Test ride as many different bikes in as many different materials as possible. For me, the key was to go to a shop where I could test ride the Ruby S-Works, Orbea, Cervelo, Cannondale,Titus and Serotta side by side. Each bike was set up with the fit measurements I provided them for the test rides. Doing this allowed me to focus more on the ride characteristics of the bike, rather than the fit. Being able to ride them each for 45-60min., often going back and forth between the top contenders was very helpful.

Trust me, I know finding a decent selection of high quality race bikes in smaller sizes is not always easy. If you have to go to a number of shops, insist that the bike be set up with your fit measurements, and take some notes after riding each bike for comparison sake.

Ignore all of the sales b.s., and take personal recomendations with a grain of salt. Find the geometry best suited to your needs.