RX packs and servo voltages

[Wingnutz]

Setting up my F-86 EDF and have run across fluttering rudder(1) and elevator(2) servos. Servos are rated 3-6v and the rx packs I'm planning to use are putting out more than 6v under load. Is this causing the flutter?

[Ededge2002]

Could you try them individual powered with an esc?

[Wingnutz]

Replaced the fluttering rudder servo with a new one and that solved the rudder flutter. I think the original servo may have been a victim of hangar damage while building...Involved re- wiring the servo with a new heavier gauge twisted extension which is a fiddly job on this model and took way more time than I'd guessed.

My servos are not HV and are rated 3-6V.
I'm presently using a five cell rx pack which puts put 6-7.5V.
Would it make more sense to use a four cell rx pack which should put out 4.8-6V?
What are the down sides to using a four cell rx pack?...pack will have to supply the radio and five 9g servos.
Thanks in advance for any advice.