Bigwill,

I basically agree, and its a minor point, but I prefer to think of one flat inflexible inclined plane, that is basically hinged on the ground (exactly where it is hinged is a little more complex, but I won't go into that!). A plane shift involves moving the whole plane around this hinge. Then when you're shifting planes your not 'between planes', but in the process of 'moving the plane'. Kind of like a door - it can be at a basically limitless number of positions in relation to its hinges (all different 'planes') but it can move from one position to another while continuing to point at it's hinges.
Chris

That sounds like the right answer - thanks.

I guess it has to be hinged around the plane line as it runs through the point of contact of the ball?

Is that right - remember we are not scared of complexity if it brings out the truth!

Thanks for your help

I think it probably is the point of contact with the ball - but others may think differently, this is just my intuitive thought (which is why I was a bit concerned about getting into this). If this is right, then it's interesting to think that as the plane shifts, so too does the low point line because of this.

I'd be interested in the thoughts of some of the experts on this (although I admit its just a technical/theoretical question which probably has little impact on how you actually hit the ball!)

Chris