Topband: 1/4 wave vertical

[cris at gm4fam.plus.com]

Greetings!

I have just put all materials together for a 1/4 wave vertical on 160m
which will be going up early next year.

It consists of a 18m grounded tower + 9m of aluminium tubing + a 12m
Spiderpole (complete with 2mm uninsulated wire).

Assuming a gold standard earth system (120 x .41 lambda radials) can
anyone advise me which of the following 2 options will work better.

a) Gamma matching the tower (with top pole assembly) or
b) Running a separate insulated wire down from the base of the Spiderpole
directly to the coax at the base.

If b) what is the minimum separation distance for the downwire from the
tower itself?

Hope someone can help!

73 Cris
GM4FAM