RHW wrote..
Most people think of The Golfing Machine plane as a huge rectangle -- and, it could be. It could also be a large circle, square, etc. Mr. Kelley never described the shape of the plane -- he only said that it had to be larger than the cirucumference of the club being swung (2-F).
If you read the last paragraph of 7-7, Mr Kelley says "Always view the Plane as retangular (with four ninety degree corners), ...."