[Antennas] Vertical and parasitic question

[ARDUJENSKI at aol.com]

When setting up a 1/4wl vertical with a director or reflector element  what 
is the best way to get them adjusted? I assume there is going to be a  
compromise between gain and F/B ratio.
 
For example my guestimate and rough run on EXNEC shows a target set up  of:
DRIVEN ELEMENT 33.4ft
DIRECTOR: 32.5ft
SPACING: 15ft
GAIN: 4.dBi
F/B 12dB
FEEDPOINT: about 15 ohms
 
When you actually set this up in the field how do you tune for best  
performance in the field? Do you recommend setting say both elements at 34ft and  use 
base variable capacitors to electronically adjust the element lengths say  for 
7.1 and 7.45 MHz (5 percent shorter so use 5 percent higher freq)? Or just  
set them up us as guestimated above? Then what?
 
I have looked in several sources and searched the web with no success. I  
would appreciate any guidance or point me to a good reference.
 
( I figure mutual conductance and varying ground conditons will play a role  
in tuning for best performance).
 
Thank you
Alan KB7MBI
Woodinville, WA