Did you try using a regular shackle and getting rid of the twist shackle? This turns the ring fore and aft, naturally unhooked. To hook it you rotate the mast into the ring and pull the sail/ring down onto the hook. To unhook you simply lift the ring and POP, it's off. It's a very cheap and simple thing to try. It works perfectly for me. Never ever a failure, up or down - not once, not ever. Tampa is the lightning capital of the world and getting a sail down quick is a way of life. "Instant down" is a must.