I have room to erect a "half square" (aka upside-down phased verticals?)
20-meter antenna to be fed at one corner (low-impedance location; attach
50-ohm coax) or at the bottom (high-impedance; use a matching network):

A B
+--------------+ 1/2wave long
| /| 1/4wave high
| / |
/ Matching Network
Coax

Unfortunately, I do NOT (because my house is in the way) have room
to make it a more-balanced curtain:

A B C
+--------------+--------------+
| /| |
| / | |
/
coax

However, if I skip the middle "vertical", I have room for four vertical
sections in a space that should have five:

A B C D E
+--------------+--------------+--------------+--------------+
| | this part will be about | |
| | 10 feet above the peak | |
of my house

FWIW, line ABCDE will be about 30 feet above ground.

I've never done any antenna modeling, and I've never had any "feel" for
antenna phasing (EE degree notwithstanding), but I suspect feeding it
at the original corner (B) will result in somewhat unbalanced currents
almost everywhere.

QUESTION: Is there any not-too-difficult way to feed it at point C,
especially without a lot of cut-and-try (since a lot of
tree- and ladder-climbing will be involved)?

What about, for example, bringing x-wavelengths of coax BC and CD to a
common point somewhere above ground level (my shack is in the basement)
and connect them with a T to the coax that goes through the wall to
the rig? What lengths?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)