UPDATE: although I'd previously posted that I hadn't had any of these hinges "fail" per se (and I still haven't), I've just run across some loose metal rudder hinges on a relatively new model that caused flutter and rudder/fin breakage.

I wasn't able to hear any flutter, but after having the vertical stabilizer pop loose in flight and the rudder break where the horn mounts, I'll surmise that flutter is responsible for this particular failure. The servo/pushrod/clevis/horn are tight, and the only slop in the system is in the metal hinges.

Again, this is a new model, barely a year old, with only 4 races worth of air time (that's not much). It's got the grey dust, and the hinges are loose. As a result of this failure, I won't use the metal hinges again.