One other issue I were considering was that even though the circuit is
built with very short leads directly on a continuous ground plane (PCB),
Some "Pads" have been made by cutting away copper. But because the PCB
is double sided, I wonder if the interaction between these pads make the
lower ground plane and pads act like a capacitor (ie. energy coupled
from the pads into the lower ground plane and up into other pads through
capacitive coupling).

Maybe if it was single sided board or I add heaps of track pins from top
to bottom layer would prove if this was the case.
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With only having double sided PCB material I drill various holes and
bond the 2 planes at different locations by soldering wires on both planes.
For VHF/UHF circuits (in addition to the above) I line the circumference
of the material by folding 6mm wide thin (abt 0.2mm thick)copper strip
onto both planes and solder. I found a 'half a mile long ' roll of this
material at a flea market .

Frank GM0CSZ / KN6WH