Sean,
What Jim refers to is a "Flopper Stopper". North sails sells them on their website
at this link. They also provided them as giveaways in the skipper bags at the J/30 North American championships we held in 2008 and 2013. A halyard is attached at the top with a line attached at the bottom that is about 1/2 the height of the headstay and connected to the jib tack fitting. A third line connected at the aft end of the flopper stopper tensions the headstay to the spinnaker ring on the mast to prevent the noise and oscillations when wind blows over an empty head foil.
![[Linked Image from northsailsgear.com]](http://www.northsailsgear.com/Portals/0/aspdnsf/images/Product/medium/FlopperStopper.jpg)