I agree with you 100% - the sweetspot plane can trace a SPL. By definition, any inclined plane traces the base of its own plane (in the imaginary sense of placing a flashlight on that plane and moving it along that plane while pointing the flashlight beam at the base of the plane). However, the sweetspot of the clubface can never travel in a straight line.
Picture the Bench Drill: Find a bench and swing back and forth.
Your shaft will stay in contact with the bench while your clubhead travels in a arc. This is a natural phenomenon.
Remember that the inclined plane lies against the bench and ALSO on the ground.
So what happens on the bench ALSO happens on the ground!
If the ground "was raised" at the bench height the result would be the same: You would dig a giant divot that would be straight in its inner part (at the shaft/hosel).
Hybrid Mode
