I also am looking for a Cannondale to build up as I have never ridden a rode bike version. I have a Vitus, 60 cm frame and I've heard and read of the frame flex but I haven't experienced it. I'm not a strong rider and at 6'3" 265 lbs I'm probably stressing the frame a bit. I love my Vitus. I don't ride it often but when I do I really enjoy the ride.