K7ITM wrote:

Is it possible to lengthen the D.E., causing it to present an
inductive reactance at the feedpoint, and match that (to 200 ohms, or
to 50 ohms) with a shunt capacitance? That may work better, giving a
broader SWR bandwidth....

Good, constructive suggestion, Tom. Kudos for putting in a bit
of design/analysis effort on this rather than just shooting from
the hip. This is definitely a weird way of driving a yagi. It makes
me yearn for the old TV-antenna schemes that used folded
dipoles for the driven element, suitably split-up between upper
and lower wires so as to give a 300-ohm terminal impedance even
with the resistance-lowering effects of the reflector and directors.

Jim, K7JEB