Just a small aside, are Stirling engines used on other spacecraft? The Wikipedia article suggests development was largely abandoned a decade ago. My first glanc

Just a small aside, are Stirling engines used on other spacecraft? The Wikipedia article suggests development was largely abandoned a decade ago. My first glance concern would be that because it's reliant on moving parts it is liable to fail sooner than a purely thermoelectric RTG (due to part wear, lubricant leaks, fatigue, etc). This would seem to be quite important on the timeline of a probe that is going to take a long time to reach the subject of its investigation. Which, to your point, only works against the idea of hypothetical Voyager 3.