Instead of a block or a proper sheave I have decided to do a 'dumb sheave' for the main halyard. This is basically a hole drilled through the mast that has been rounded of so that the halyard runs smoothly. I tried with a file but it took so much time, finally I found a monster bit for my drill in the toolbox. I have no idea what it is intended for (or when I got it) but it cuts through wood like butter (very cold butter). Then I cleaned it up with the dremmel. Thinking of putting a strip of fiber glass in there for abrasion resistance. Finally I sanded the mast with the orbital sander (did a bad job with the plane this time, too lazy to sharpen properly).