I have setup numerous Futaba SBus/Cortex pros in jets and in a warbird using a full SBus setup and have never seen this centering issue.
Why it goes away when using the harness is puzzling.
Regarding the gittering when the motor is at certain RPM we saw that on a friends Havoc SS. It was mounted to laminate of FRP, wood, FRP. He made and acoustical hood of foam, issue resolved. Using only plywood has much better dampening qualities.
Every install issue can be different but can be resolved.
Last edited by Bob_B; 02-27-2021 at 08:43 AM.