Deduct a minimum of 9 inches for the Sail Luff Length.
All you need is the measurement from the where the wire goes into the Top Stud of the Turnbuckle top to the very top of the wire where it attaches to the mast.
To accomplish this while on deck mast up, use a Jib Halyard line attached to a shackle around the UNOBSTRUCTED stay wire, with a messenger line attached to prevent it from staying aloft and also act as your measuring line.
Carefully hoist the shackle up until it reaches the top. Be careful not to snag it on anything.
Mark the messenger where the wire goes into the Top Stud.
Now bring the halyard down and measure the messenger line.
Rather have us do it?
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