When I built my Giant Aeromaster, powered by a G-62, I installed two HS-81 servos right under the cockpit. One to control the throttle and one for the firewall mounted kill switch. Both used nyrod push rods. They both failed within 4 flights. Seems that the very fine wires on the servo motors could not take the vibration. I replaced them with HS-425s and never had another problem.

While at Bomber Field in September 2004 I was talking to BB Weber about the problem. Seems that he was using HS-81s and all 4 had been knocked out by the vibration of the engines on his big Bear bomber. These were mounted in the nacelles. The engines were alcohol fueled. I don't remember him flying it in 2004. By 2005 he had put standard servos in and had a beautiful flight.