I am not familiar with the CAV loaders specifically...
Does it have the "tri-roller" support on the back of the head stock?
If so, the lengths you are specifying sounds like the area your pusher would be transitioning from the loader to the machine.
At that point, some time before, the "tri-roller" would open to allow for the pusher to pass through.
This would cause the vibration untill the pusher made its way into the spindle.
Just some food for thought.
Let us know how you make out.
Good luck!
Control the process, not the product!
Machining is more science than art, master the science and the artistry will be evident.