I just bought a 1976 Oday Rhodes 19, centerboard model. It has a tapered mast with halyards running inside the mast and exiting at the foot of the mast through two sheave blocks. I'd like to consider putting in a tabernacle, but I'd have to move the sheave blocks up above the cuddy, which would require cutting a rectangular hole in the mast for the double sheave block. Anyone had any experience with this? I'm worried about weakening the mast.