Patrick,
I don't know about the other builders, but Masi generally did the change at 59cm also, IF it was Columbus tubing. Most Masis from about 1972 or so are standard gauge Reynolds tubes, and there was no change in the larger sizes except in special cases where a heaver down tube and/or chainstays were used.
Brian Baylis
La Mesa, CA
As I wander through the acquisition maze that is ebay, I find that this question sometimes stops me from bidding. I can ride a 57, 58, or 59 c to c. I love SL and some SL SP combinations. but all SP beats me up too much on long rides! I know from the archives that Medici , for example, went to all SP at about 59, so I did not bid on two of these that were recently up. So the question would apply to Masi, Colnago, DeRosa, Gios etc. just toward the end of the timeline. I know as the 80s progressed there was more danger of getting something with a harsher ride as the dastardly bike magazines all seemed to decide that racing bikes all had to be criterium ready with upright angles, unyielding tubing high, bottom brackets, and hairtrigger handling. I know that the US factories and the Japanese bent to this fad, but what about these and other Italian builders?? Thanks..Patrick Lay in Chicago