Topband: HiQ antenna question

[Sam M]

Hello to the list,
I just joined and have a few questions for the list.
I live in an apartment complex.
I will be placing a Hi-Q 5/160 antenna on the roof in the near future.
The roof at 20 feet and is tar and gravel.
I will have a ground radial field laying on the roof in my only clear area.
There will be 16 radials each 13 feet long attached to a metal plate.
The base plate is 18 inches by 24 inches
with the antenna mounted in the center of the plate.

The 5/160 antenna
http://www.hiqantennas.com/HiQ5160.htm

will have a 1 foot (1/2 inch diameter) extension
above the coil, then the EB-8 top hat above that.
http://hiqantennas.com/
scroll down the page for info on the EB-8

I plan to add a 102 inch stainless whip on the top of the EB-8 top hat

if I do I think my range of frequencies will be from 160m - 30m
if I only use 82 inches of whip I would be able to have 160m - 20m

so my question is would I lose any discernible signal strength on 160m if I were 
to sue the 20 inch shorter whip.

I realize I may only be getting about 1.3 % efficiency any way
so we're talking about (maybe) 1.3 watts out with 100 watts in.
So would the extra 20 inches matter?

I don't mind loosing 20m, but if it isn't going to make a hill of beans worth of 
difference on 160m .........

TIA
-- 
GB & 73
KA5OAI
Sam Morgan
http://linuxbasics.org
Linux, the lifetime learning experience.