how tall are you? what are your measurements (inseam, arm length and torso length)? for starters, the measurement you should go by is the top tube length. many websites have fit estimators, competitive cyclist being one of them. i don't want to scare you, but carbon snaps quite a bit easier than aluminium does, although if you crash at 30mph, chances are, you'll break any type of material. you should be prepared to part with $600 for an used frame as an insurance policy