John,
If I remember correctly the S64E did not have the yaw function on the back seat controls but the S64F did. I remember riding left seat while setting a radio antenna and the back seat pilot had to ask for yaw adjustments from the pilot flying the right seat. I could be remembering it incorrectly or it may have been something operator specific. I would swear there was some differences though between the E and F model cranes in regards to the back seat controls.
Max