I wouldn't recommend using a 3004 on the rudder. That servo makes 40-50oz of torque, and you need something with 90-100 or so on the rudder. I've got a Hitec 5625 digital for my rudder and at 6 volts it makes 130oz of torque, and is fast too at .14 sec/60 degrees. Even at 4.8 volts you'll still have 109oz and .17 on the speed. Street price isn't too bad, around 50 bucks.