Hi Tom, When I had to rebuilt my new mast last year, I used the old mast top fitting with the two sheaves. On my old mast, the wire halyard had been rubbing on the forward side, because the sheave wasn't located properly. Since I used the old mast top fitting on the new mast, my first job was to relocate the sheaves. Luckily, I have an aircraft parts shop I work with, so they welded the old holes closed, and then I drilled new holes for the sheaves that were further apart; i.e., the halyard now was completely clear of the top edge of the mast on both the forward and aft sides. No more chafe! At the same time I converted the main halyard to an all rope halyard. Connie