Chuck,
I just recently finished a round of antenna tuner thrashing that
included some vertical, half wave wire, bottom fed antennas... This
was through a tuner(s) of my own design and construction including
hand built variable caps, with the feed points being head high and
the 1/2 wave antenna worked against a half wave elevated counterpoise,
with the coax dropping straight to the ground and running on the
ground hundreds of feet to the shack...... The ground was wet with
half melted snow and rain during most of the test... I had to stand
in a flowing stream to make tuner adjustments - snow melt water will
get your attention when it runs over the top of your boots!

While I got the tuner design to work - which was the whole reason for
the exercise as opposed to being primarily an antenna test - I was not
impressed with the half wave, end fed, vertical antenna overall - 80,
40, and 20 meter antennas were tested...
They were distinctly more noisy than ground mounted quarter wave
antennas for the same bands... Often, deafeningly more noisy...
The recovered signal strengths we
1. often less than for the quarter waves -
2. sometimes comparable -
3. the strong signal exceptions being the times that the very low
arrival angles were exactly what the half wave vertical wanted to
see...
(you can never have too many antennas)

On 20 meters the separation between the two antennas was 500 feet,
and expanding to some 900 feet for 80 meters test antenna being the
half wave end fed, and the reference antenna being 1/4 wave ground
mounted... I feel that the distances were sufficient that mutual
coupling was minimized enough as to not skew the results - it
certainly was not eliminated, however...

The circulating tank current on a tuner used transform 50 ohms to an
end fed half wave is impressive - often melting the dielectrics used
for the variable caps...

denny