[EdZ]

As mentioned, the key is the right elbow.

Keep in mind that startup swivel does NOT mean just letting the left wrist turn on its own per se.

It is the entire power package that is effectively turning - due to the right elbow being in a pitch position - with the right elbow staying relatively in the same place during startup.

By contrast, a hitter's power package doesn't rotate, because the right elbow does move during startup, back, up and in - along the line the right forearm is pointing at impact fix.

In both cases the shoulders have to move to maintain the structure of the power package and the flying wedges.

For the swinger, plane line tracing and not 'covering' is the key to preventing an over swivel. Often an over swivel is the result of trying to cover the plane line with the clubhead, rather than tracing it with a 'beam of light' extending out from the shaft.

Back, up and in.