I strickly believe that the THE TOP OF THE SPINE (base of neck) is what should stay 'STILL'.
If the entire head does the golfer will wind up with a whole bunch of funny looking 'positions' that make controling the machine very dicey.
Also the neck should be parallel to the ground at address and impact interval for correct hinge action.
Brian's point is well taken. And certainly individual capabilities andpreferences must be accomodated. The Big Picture is that, in addition to theStationary Feet, there must be some point on the Pivot held fixed in orderto insure a Centered Motion. Homer chose to use the Stationary Head forthat Center and listed it as the First Essential (2-0). However, a"between the shoulders" Pivot Center works just as well and probably,as Brian suggests, in many cases better. It certainly tends to get that RightShoulder moving -- and hopefully, the Right Hip. A 'Two Birds with One Stone'kind of thing. Homer offers that alternative in the Glossary under the'Stationary Head' definition.
Brian's point about the "the neck should be parallel to the ground ataddress and Impact for correct Hinge Action" is not a concept addressed inThe Golfing Machine. Therefore, I would very much like to learn -- keyword is learn -- why an excellent teacher of many years experience feelsthis to be the case.