I bought all 6 of my carbon bikes used and while I've not had any issues, I'm just some guy on the Internet and whatever I say might not be enough to assuage your apprehension towards buying used carbon. It's a risky exercise; I just look for obvious cracks in the joint areas, do some tapping along the tube. If I'm buying sight unseen from BBB or TPC, I feel more assured that they've inspected it thoroughly, plus they have a warranty/return period IIRC. In the 2000s, I feel the general thinking was that one little scratch on your carbon bike might make the thing unsafe to ride; nowadays carbon manufacturing has come a long way and they get abused plenty in MTB and CX applications, and I think people now understand that scratches and scuffs are no big deal, and even with big cracks, carbon can be repaired.
The part about fit, I've gone thru enough bikes now to know a good fit from a suboptimal fit. On frames that are one size up, I could always make them work but it's never perfect and I seem to not be able to put out as much power.
Last edited by tFUnK; 03-23-24 at 04:34 PM.