Tony,

Both Vernon and myself are using 5 cell packs. I have not had a problem with mine but they were the replacements I got from Horizon. All 4 of the servos that failed were purchased at the same time. Both servos are set up on a Y harness and are going through a JR 450 gyro. I have not seen any technical spec that says not to use them on 6V so I am assuming that is not the problem. I also set the servos up where the linkage is giving the optimum mechanical advantage. FWIW yesterday these servos failed when testing the smoke system on the ground. The first failure also occured with the plane on the ground, and the second failed sometime in the flight. In all cases the servo failed hard over.