If you change the saddle setback you would have no problems getting the right fit KOPS wise with a 54, 56(assuming this is your *ideal* size), or 58cm frame. Same for reach. The only thing that is a *real* issue is bar to saddle drop when you change frame sizes. Again, 6cm is only 2.36 inches! If you take a look at the 56 and 58cm CAAD10 frames the TT is just 1.5cm longer on the 58!