I can testify to the low efficiency, however, as
the shack is comfortably warm.

At this time of year, that's a great advantage of a linear amplifier.

 

Just curious whether anyone has considered an envelope elimination and recovery design.  One keeps the switching mode RF amp and adds a switching mode "modulator" in place of the power supply, plus circuitry to extract the envelope of the waveform and the RF drive separately.  It could become quite elaborate if one wanted to achieve commercial specs, but I doubt that it would need to be quite that refined for satisfactory PSK performance.