I use goop. I put a tiny dot of goop on the back of the feather quill about 1/8"-1/4"up from the tip. I then put a small piece of wood (cut from the end of a striker, etc.) about the middle of the feather to weigh it down and let the glue dry a bit. After about an hour, you can remove the piece of wood, or whatever you use for weight, and the feather will stay in place. You won't have issues with the chemical haze that some glues make on the bottom side of your glass using goop. As little glue as it takes, it does nothing to dampen the sound of the call.