Another possible option that may work, depending on A/C models and controls, is adding heat strips to the two air conditioners. From one manufacturer:
•Optional Heater Assembly can be added to provide a source of warm air.
One advantage to heat strips, if a viable option, is that they would use the existing 20-Amp circuits to the two A/Cs.
A quick search on different forums shows that some owners love heat strips and others prefer portable heaters for various reasons. I'm not even sure if they can be added to ducted A/Cs, but would consider it.
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