I have the DS811s all round and the DS8231 on rudder. I had terrible jitters on the elevators. Backed off the screws, made sure the servo wasn't touching the side anywhere and seen that my linkage was 1 to 1 and it stopped. They say that the centering is so accurate that any slop or bind that it will fight itself to center. Or I may have done something that I just didn't realize, but it stopped. Joe