From my past experiences I say run both a TR spring and a failsafe. I have had 2 run aways now and will never run again without these safetys in place. Too expensive and too dangerous to not run them. I figured I would never have a problem.. Ya right! You'll see when it happens... Not a good feeling. The TR return spring does load the servo a little more but works fine. 6V is a must for the receiver.