But the point is still this:
It's a waste of time trying to calculate the perfect node.
Clearly, as you move up and down the string, the pickup will capture a different set of vibrations. But to say that the pickup "must be in position X to capture the tone of that node" is just silly.
Why?
Because as soon as you fret a string, the node moves.
If you make two identical guitars, one 22 fret and one 24, and place the neck pickup at the base of the neck, obviously there will be a minute difference in sound. The 22 fretters "octave node" should be right above the pickup, while the 24 fretters "octave node is before the pickup. As soon as you fret a note, the 22 fretters node is now being pushed passed the pickup, while the 24 fretters is being pushed onto the pickup.
Not that any of this really matters, as the pickups field isn't that narrow anyway...
Voodoo.