I'll be using 6.6V A123, It appears the S9551 may be discontinued. Not on towers or Futaba's website. But the other servos look good. I am not a JR fan, seen to many with loose gear train and I use Hitec titanium gear for my 3D and IMAC but they don't seem to center very well even with a narrow dead band setting. So looking into Futaba. Also, someone mentioned Hyperion servos, although I have no experience with them...