I just had a professional fit done a few weeks ago. The fitter changed the stem and seat post. He also told me that he would not disagree with the fact that my bike may be one size to large. I did not mention that I was thinking about a carbon frame at that time. Cannondale has this program that allows you to upgrade to a better frame for a price. The price is around $1,350 for an SL frame using my alloy frame as a trade in. I would use my current parts to complete the bike. I am not sure what a complete bike would cost with my bike as a trade in, probably much more than that.

I haven't checked the price on a 58 alloy frame.