but the one thing about Jon's setup I don't get is how the halyard is guided so it doesn't put side loads on the sheaves. Without guidance the halyard will chafe on the sides of the sheave box. (e.g. -- look at the swivel-mounted block just about the genoa's anti-wrap collar in the photo below. It allows the spin halyard to be pulled off to the side without deviating much off center as it exits from the sheave above).