I could have sworn I responded but can't see it now. I test rode a 60 cm CAAD9 and the 61 cm Synapse. The synapse was definitely a more comfort oriented bike, to be sure. At 6'5" though I must be all torso or something. The Synapse was too large for me, the 60 cm CAAD9 was a great fit, the 64 would have been way too big. Especially since I needed to add a zero setback seatpost to the CAAD9 due to the shallower seat tube angle. The size 64 vs. 60 has a shorter reach, just a shallower seat tube angle for more setback and longer effective top tube. The CAAD9 has the same geometry as the Super Six. I bought the CAAD9 and it still fits me well.