Okay, good news first!
It seems that the world data itself has converted mostly correctly! I've restored the whitelist so 709 can start thrashing things again.
Then the less good news!
Along with rest of the dat files, all of the maps have been wiped clean.
That's gonna be fun to rebuild.
Signs have some occasional garbage text in them. Not sure what caused that, but we can fix them as we find them by just tearing them down and reposting.
Many of the "command button" contraptions around the world are broken. I'll try fixing the transporters around the Enterprise and the armor-givers around Bradtropolis (and in my attic).
I also used this opportunity to upgrade Java from 1.8 to 1.11. Maybe that'll make things a little smoother or faster? I wouldn't bet on it.
If things actually get less stable and we suspect Java is the culprit, it's not hard to downgrade to 1.8.