Just to throw out another idea or two... Does your marina have a Travel-lift? If so, you may be able to put your boat in the well to help reach the masthead w/o going aloft. For a couple of bucks (more likely a 12 pack) you may be able to get one of the guys at the marina to lift you with the Travel-lift or a crane while your boat is in the well.
Never hurts to consider other options that might be more comfortable and safer.
hunter Legend 37 Semper Paratus
Formerly - Tartan 34C Yawl