[MizunoJoe]

The problem with all this is that the shaft (or more exactly the sweetspot line) doesn't move on the same plane in the BS and DS in any effective golf swing I've ever seen. In fact on the BS, the shaft traces out a curved surface. A look at the latest edition of Golf Magazine's sequence of Ken Perry will show you that even in the some DOWNSWINGS, the shaft traces a curved surface.

Better to put lasers out the butt of the shaft and pointing from #3 PP to the plane line just in front of the leading edge of the clubface. This, at least, allows a diferent "plane" for the BS than the DS.