Just a comment -

The design, from start to finish, of a linear power amplifier is based
solely on a device's ratings - volts, amps, watts, etc.

Its RF internal impedance plays no part in it. At HF it is never specified
by the manufacturer.

Even ARRL bibles don't mention the subject of Rint. It's superfluous. Does
anybody know what it is? Give us some numbers.

As for conjugate matching - don't make me laugh.
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Reg.