Here's a recommendation I saw in Good Old Boat magazine last year:
Put a permanent tail in the leech cringle by eye-splicing a piece of braided line. How long piece? Long enough to do what it says ya gotta do with it! (Read on.)
Then find the middle of a single continuous sheetline and mark it with whippings about 18 inches apart. Form a bight with the part of the line between the whippings and use the tail to secure it with a double sheetbend.
Advantages over single sheetline with cow hitch: no wrinkles in the clew and you can change headsails while leaving the sheetline in place.