Topband: Seperation of Radial Ring vs Vertical

[Bill Gerhold]

Knowing that the feed point of a 1/4 wave vertical
is a high current and low voltage point, I have this
question to pose.

How close/far can one position the vertical (radiating
element) in relation to the radial ring?

Is it ok to have a seperation of 1 inch?  12 inches?
So forth and so on.  I have not seen this subject discussed
either here or in any of the popular antenna books.

My 1/4 wave 80 meter vertical is currently seperated from the
radial ring by about 3 inches.  I would like to increase
this to about 6" by using a new insulator.

Is there an optimal seperation distance?  How far is too much?
What would be the performance effects of having a vertical element
incrementally increased from the radial ring?

Thanks
K2WH