[TowerTalk] Shunt-fed tower radials

[KI4JWY]

I am in the planning stages to shunt-feed my tower for 80 & 160 meters. 

My tower is a a 70' Rohn 25 G with a Hy-Gain DX-66 6 meter 6 element beam on top. The tower is located at one corner of my house on a lot that is 100' x 130'. I can run radials in a 270 degree arc with distances from a minimum of 50' to a max of 135' from the base of the tower.

I have a copy of "Low Band DXing" I have been reading. I am thinking about building a radial plow and use "electric fence wire" for radials.

My question is how many radials and how long? 

John
W0TMM