Topband: 160M ant advice

[Robert Harmon]

I am planning an install of a 160M inverted L  and would like critique 
from you top banders.
I was originally planning a separate tower for 160 but my XYL has 
squashed the idea  :-)
My tower is 90 feet fully extended with a 18 foot mast currently used 
for a Force 12 WARC plus 10/15 beam
on top and a N6BT DXU-32, 2EL 40 and 3EL 20  12 feet below.
At the top of the top section I have a 10 foot fiberglass pole I plan to 
extend out to support the vertical, so it will be 10 feet away from the 
tower.
I am thinking of feeding the vertical and having 4 elevated radials at 
the 14 foot level.
So the vertical wire will about 76 feet long.

I am wondering if I would be better lowering the feedpoint & radial tie 
ins down from 14 feet say to 8 feet and have more length in the vertical 
portion of the L or better to have the 14 feet elevation for the radials ?

Also the horizontal leg of the L on top will be about 5 feet below the 
40/20 yagi only 10 feet out from the tower,
do you think this is OK as far as interaction between the yagi and the 
160 L ?  Anything else I should consider ?
I have never had a decent 160 antenna, just hoping I can work something 
out with my existing situation

thanks in advance,

Bob
K6UJ