I don't think you could control the machine with one servo flap missing. Between being pretty out of balance, the flap also controls the flat pitch/auto RPM setting, one might be able to lower the collective and find the spot where all the blades be somewhat equal, but changing collective settings causes the aircraft to pitch quite a bit because of the rotors are angled away from the fuselage to the sides and thanks to gyroscopic precession the thing pitches fore/aft.