How about black streaks going all the way back to the end of the control surface?

I've run several of them for years, and none have failed yet. They get loose, but I don't remember having one break. The high nitro and resultant vibration from a YS don't help matters, either. Mine are in Gold-class warbird racers (also World ARFs), and suffer far worse treatment than they would in a 2-stroke powered World T-34.

Nonetheless, they seem to work, and the best part is that you don't have to glue them in to begin with!