Toroid Proximity (was Primary Design)

Hi all,
        In Richard Hull's reply he said...

> We have also recorded and noted that there is a critical distance
> from the secondary where the toroid shifts from a Q booster to a Q
> destroyer.  This is undoubtedly related to its effect upon the top
> of the resonator coil.

Having done a lot of measurements last year I was interested in this.
I went to that Nat. Geo. article and noted the toroid and the height
it was placed at. I also noted a similarity in the height and where
I scored the best Q's with my terminal heights.
    Q. - Would you mind quantifying what you found with reference to
this coil re terminal height placement?