The paralllel to the plane angle theory that Hank Haney adheres to is a "parallax" problem that is the result of an out of position camera...Tom Ness did a great article for Golf Digest that hasn't yet been approved...He fillmed the same swing withe three different cameras postioned at different place along the plane angle all facing down the line...the results were three different looks to the same swing.....
Yeah, I always wondered why something that violated one of the Imperatives would not be " deemed improper".
David Leadbetter taught this congruent plane stuff back in the eighties. He called it " riding the plane ".