Hi,

I have used both the JR 3421SA and Futaba 9650 (the equivalent) on 2m F3A glow models. All I can say is that 9650 has slope from the first flights which becomes bigger due to vibration. 3421SA has a lot less slope and is a very precise servo. Now it has been discontinued I think.

By the way I think SAVOX makes a similar size servo which for sure worths a try as it is slope free.

FYI I fly Futaba so I am not JR biased...

rgrds,

Nikos