RE: 545 centering
These servos are utilizing standard servo amplifiers and 5-pole cored motors. They do center better than other 3-pole cored motor servos. However they are inexpensive sport servos with enhanced performance, accordingly they will never center as well as a precession coreless servo and or a digital servo.
I'd suggest they should not bounce once they stop, BUT there are things in play that might cause the anomaly. Make sure there is no binding and the surface moves freely. If you’re concerned return the servos to Hitec for a checkup...