This 1/16″ x 1″ Cotter Pin is a standard keeper for the Flying Scot.  At the factory we butterfly them at the top of the forestay and at the top and bottom of the shrouds as those are only removed when replacing the stay.  They are also used on the forestay with the clevis attaching the forestay to the extension.  Another option for keepers that have to be removed more often is a split ring.