IMO You need to use a RETRACT Servo. The Futuba S136G, Hitec HS-75(the ones that I've been using), or the Hobbico CS-63 are all good choices. These servos are designed for mechanical retracts and do a good job. Lots of torque. Mind you, each of these servos is not adjustable - they move through 180 degrees of travel (Stop to Stop). The 3004 would not have the strength to do the job. The Hitec and Hobbico only run about $30 each new from Tower. I just picked a Hitec HS 75 on RCU for $10.