Jake, my rudders have never hummed (although my daggarboards sure did around 16 kts and again at 22 kts GPS)

I opted to take the last 1/16" and file down one side, leaving the other as is. Not knife-edge sharp, but flat edge at the back.

My thinking is that this small fairing now makes the shape slightly asymmetrical, and therefore less likely to produce any harmonic vibration.

I've tried to do the same with the daggars, with limited success (keep getting nicks in the trailing edge from where it rubs the daggar-well when we hit stuff)

Of course, I could just be some kook sailor who is lucky enough to not have his rudders hum..