I personally don't use a FB, but my brewing buddy does. He bought some 1/4" silicone tubing, cut a slit in it, and put it around the diameter of the FB. It creates a perfect seal and keeps the FB in place.
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - Kane-DOH APA (Honey Citra APA)
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Raspberry Florida Weiss
Keg #2 - Cinnamon Raisin Cider
Keg #3 - NONE!
Bottled - NONE!