Dr. Slick wrote;
"Well, our super J-pole is bearing our yagi in ALL directions, even in
the forward lobe."

It`s possible.

This thread pits a "Super J-Pole" with 6 dBd gain against a "Yagi-Uda"
with 2.85 to 17.85 dBd gain (5 to 20 dBi), depending on construction.
So, it could be true for some 2-element Yagi or it could untrue for a
Yagi with 3 or more elements. A 3-element Yagi may give about 5 or 6 dBd
gain.

The "ARRL Antenna Book" gives the details. In my 19th edition, the Super
J-Pole is asid to give 6 dB gain over a 1/4-wave whip on page 16-27.

The whip with a perfect reflection (a ground-plane antenna) is said on
page 13-10 to be equivalent to a 1/2-wave dipole in free-space: "---the
image of a vertical antenna is in phase with the vertical radiator". The
whip with the perfect reflection is thus identical to a 1/2-wave in
free-space in performance. Gain of the ground-plane is 0 dBd or +2.15
dBi.

Best regards, Richard Harrison, KB5WZI