a beautiful boat should sail forever.
Hi Jim - hope you feel confident about the taper! If you use the search up in the right hand corner you will find several mizzen staysail references. Probably the one by Clyde might have some useful stuff.
Let me say right off: The running back stays are a part of the mizzen staysail installation. They are only used for that sail.
Secondarily, here is the drawing I made "back in the day" when I was installing such things. Note the little picture in the lower right hand corner about securing an unused running backstay. Take them off and store them, and the hardware for securing the backstays when not is use can also be removed. Take a sail for me!