[TowerTalk] Allowable antenna area

[Dainius]

Hello

I have a Rohn 25G tower height 100foot. I am little bit confused about allowable antena area.  I can put either 15 sq.ft "round member antenas" either 9 sq. ft "flat member antenas" according to datasheet. Sorry, but I can't understand this expresion - what is the difference between "round member" and "flat member"?. I want to put yagi beam on this tower. Shall I count on 15 or 9 sq ft. figure?

Thanks

Dainius
ly4oo