Simple solution
All you had to do was ease sheets and stop the boat so that there was no load on the rig. Make sure you have room to drift to leeward and tie a light line to your tools so you don't lose them overboard.Now add a full turn to both turnbuckles, then sheet in and sail off close-hauled. If the sag in the leeward shroud is gone, your problem is solved. Check the other side by coming about onto the opposite tack. If you still see some slack, stop the boat and repeat the process.In reality, the numbers, i.e. the amount of load on the shrouds is not as important as the response of the rig. If you see slack in the leeward shroud then you don't have enough tension...it's that simple. One caution...make sure that your rigging and end fittings are in good condition. Inspect at the beginning of each season. Happy sailing.PeterH23 "Raven"