"Many recommend tuning at a lower power. This risky as well. That is because at lower power, the output impedance of the PA will be different. Once you are tuned at QRP level, increasing the power will result in a mismatch again! "
Interesting. Every auto tuner manufacturer's instructions I have ever seen recommend that you tune at low power. I have a remote auto tuner at the base of a wire vertical that I tune on every band change. I have always tuned with low power using several different rigs over the decades and never noticed a change in SWR. I'll pay closer attention, but if I'm getting a change it has been to small to notice.
Haven't received my sBitx yet, but it looks like there's room for a small board with SWR sensing and an absorptive bridge that you could manually switch in and out. If you wanted to get fancy you could route the measure to the Pi and integrate into the display.
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??? Bob? KD8CGH
Bob Benedict, KD8CGH