Nice gripping read for an old Commander owner, DHP. I just sold my old 520 and the new owners will fly her from California to Siberia next month. I wish them the best of luck. They like old GO-engines over there because they can run on Mogas. No such luck with the GTSIO's.
I almost bought a 685 as an upgrade - I wanted the range and the pressurisation and stay true to Commanders. But in the end it made very little sense for someone who flies mostly alone. I bought an Aerostar instead. But I will always love Commanders. And if someone develops a diesel STC for these sometime in the future, I might just come back to the 685.
Best of luck with the fire breather.