RE: Tail Servo Fluttering!!!!
Things to try:-
Do they still flutter without the extension cords? If not then,
1. Check battery voltage under load. Try 5 cell instead of 4, or vice-versa.
2. Fit ferrite ring cores around tail servo extensions using ~3 turns.
3. Use servo isolators/amplifiers on each tail servo.
Oh, and those digitals will likely buzz a little normally, but shouldn't be enough to make the surface flutter. They will need a battery capable of supplying large peak currents. i.e. not just a little AA size pack, whatever it's capacity. NiCds can usually supply more peak current than NiMh in this duty. Try a Sub C pack just to check yours is adequate. Sorry if I'm preaching to an expert.
--
Steve