[TowerTalk] hexagonal beams and height above ground

[Jim Hoge]

Has anyone modeled hexagonal beams with regard to height above ground? I am very leery of the statements that they perform better when lower to the ground, specifically that on 20m, a height of 40 feet is best. I think Gotham antenna when advertising goes against the norm. I have seen a few elevation plots but wonder what is at work to make this fly in the face of convention.

tnx,
Jim W5QM