The concept for the Slot, to facilitate mast raising, came to me a year-and-a-half ago. The idea of the Plug, to fill the slot and hold the mast upright, was part of the original concept. How to hold the Plug in place took a while to figure out. Here's what I came up with:
One more design element is, what i call, the Mast Block. My intent is for the block to help support the mast (although that may not be its primary purpose) and to provide an anchor point for the foreward ends of the cockpit coamings (probably its legitimate purpose) and the downhaul. It is a work in progress.