Problem with Rigidbody Parent/Child Relationship with "Teeter Totter"

Hello everyone, I've run into a problem trying to create a rigidbody driven "teeter totter" system (A system in which the Parent is the center pivot point which controls rotation of the "plank", but the plank needs to control the rotation of the pivot point (so its a case of the child needing to control its parent's rotation)). So essentially the problem is that the parent is the object that needs to rotate, but isn't the object that the player actually comes into contact with.

The problem is, the even with a system and script that gives control of rotation to the parent, the parent object is still getting pushed around in space (and is pivoting according to the Child's position).

Take a look at my totally not terrible drawing to see what I'm getting at (hopefully):

Note: that even when locking all necessary position and rotation changes, the pivot point is still getting pushed around in space.

-The top left is the ideal setup, where the tetter totter is activated by the plank, but control of the plank's rotation is actually controlled by the pivot point. But note on the right side, as the plank rotates, the Parent is actually getting pushed off center by the child.

Any ideas on how to fix this is appreciated.