John Smith wrote:
Agreed that adding a 9:1 balun (impedance match) will have little mismatch
loss at x and all the Tx power will be "presented" to the antenna port.

Oh Boy, I really screwed up. Replace that 9:1 balun with a 1:1 balun.
I was very stupid to have said 9:1. A 9:1 balun would reduce that 50
ohm Z0-match to 5.56 ohms thus creating a mismatch.
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73, Cecil, W5DXP