Originally Posted by memebag

I rode 1 century on a more upright frame, then 4 centuries on a CAAD12. The CAAD12 was more comfortable for me. I don't have it super slammed or anything, but I'm definitely more aero on the CAAD12.

My guess is that my core was strong enough to start with when I bought the CAAD12, but that bike has kept it strong, or maybe made it stronger, so I feel comfortable with a flat back for 100 miles.