The cables only need to be tight enough to take up the slack....not so tight that they sound like guitar strings. So if you pluck them they should just make a thud sound not a "boing". You can hold the rudder at center with your left hand, then move the servo arm with your right to see how much slack the cables have. They definitely should not droop at center. This will cause the tail to wag at higher flying speeds. The servo should not sing at all at center. I just tested my 88" Yak with the same servo and it's silent. The elevators buzz a little due to the servo holding up their weight.