Anybody having problems with the real small Spektrum servos on 6 volts and a Jeti receiver?

My JR servos (and others for that matter/analog) are fine, but these mini digital servos are jittery and horribly "toothy" for some reason. Maybe they are only truly happy on 4 volts? They are the H3050 Cyclic servos for mini helicopters; just what they had at the hobby shop.

Was wondering if the Jeti had anything to do with it...tried changing the receiver output, but no effect. Not a big deal; just would be convenient to use the little buggers I have already.