Buy good quality servos ! The difference is night and day between the medal and plastic geared models .

All may seem fine with the plastic servos until they actually get used in a prop . You can waste a lot of time messing with code settings and just getting frustrated . Settings adjustments can smooth out some things but not all and definitely nothing like replacing the servo with quality . The old saying holds true .
You gets whats you pays for !

Give a listen to this servo compared to the plastic servo I used in the skull .