I've heard of people cutting the headtube lengthwise, then they spread the tubing to get it to the diameter they needed, then weld in a piece of metal the full length of the headtube to fill the gap.
I've heard of people cutting the headtube lengthwise, then they spread the tubing to get it to the diameter they needed, then weld in a piece of metal the full length of the headtube to fill the gap.