I've just replaced two JR 3421sa elevator servos in my Leviosa,as an experiment, with two Savox SH1357s.
( 2.5Kg/cm,0. 07 secs/60degrees, at 6.0V).
My guess being that something like these might make all those snaps in F11 a little less trying...
The Savox servos are very similar in size to the JRs,just a very small enlargement lets them slot straight in.
They centre well,but the torque could possibly be a bit lowthey don't seem particularly fast in the airperhaps the Savox SH 1350 would have been better(4.6Kg/cm, 0.11secs/60degrees at 6.0V)