As I understand it - with a 126 mm rear dropout, the opportunities for fitting in a 7-speed are limited (without spreading the frame), and would require some dishing adjustments. One of my riding buddies told me that you can rearrange the spacers (which implies a dishing adjustment is needed) on a Campy tipo hub to get it to fit a seven speed. Not sure if there are other makes of hubs where this could be done.