Do not use S3003 or S3004 servos in helis. They will fail.
Their design doesn't handle vibration well.
From Futaba's site:
"Both the S3003 and S3004 use a direct drive potentiometer. What that means is the output gear is connected directly to the potentiometer. Since the output gear is connected directly to the pot it is very possible that vibration will damage the pot. This is why we do not recommend these servos to be used in helis. Helis generate a very high frequency vibration due to the high rpm of the engine and the close proximity of the engine to the servos."
For hovering and FF and possibly light aerobatics S3001's would be fine.