Flutter
Adjusting jib lead positions or the vang should NOT be used to reduce leech flutter. You SHOULD use the lead position and vang to adjust the trim of your sails to properly suit the wind speed and direction.Then, if you still have leech flutter, then use the leech line just enough to stop the flutter, and ease the leech line off once the wind eases up otherwise you will have too much "hook" in the leech.Leech flutter disturbs the airflow and slows you down a little, but more significantly, it is really hard of the material and stitching of your leach. If you cannot stop the leech flutter with the leech line, then you may need to take your sails in to see if a sailmaker can help.