How high should the apex of your drop shot be?

Gold medalist Jennifer Lacore and her dad Bob Youngen are giving a clinic in Kelowna on July 6th.  I believe there are still openings.  One of their clinic topics is the third shot drop and they will talk about the "apex" of the shot, which should be over the NVL.  Another 5.0 player, Prem Carnot, has posted the following graphic showing how high this apex should be.