RE: 2 Post flight questions..
Pete,
I would agree with Todd, the centering could be the issue. I have used DS3421`s in many jets and its a superb servo for that job. I am running them right now on ailerons and rudder in my FB Mig-21, 100flights and counting. My Tams A-4 has 3421`s on every surface and 140flights with no issues, my BVM F-86 the same.
V..