I am going to buy a Masi CXR - the bikes I tested had a frame size of 58cm and 56cm (not CXR's). The 58 was definately too long, I was too stretched out. The 56 felt great. The CXR is available in 55,57, etc sizes. Should I go with the 55 or 57cm frame? Which would be easier to make fit? Does it really make a difference considering I can change the stem and seat fore/aft location?