SKevo problem was that forums weren't rsynced in the end, as you might already know).
Yes, but that was just a time and fixup issue, easily resolved. In fact I've found it's better to wait for most of the server side work on all the forums to complete, before adding additional loads by fixups etc.. In fact I say to my users, just wait a few hours before you try and use the forum again. Certainly runs very snappy now it's upgraded, almost instant responses.
It makes me wonder if it's actually worth shutting down all external server access to forums until all databases have completed, it might well be faster that way? A simple message of forums being updated would suffice to inform users.
P.S. As for disabling extensions, I've a suspicion think certain ones need purging before disabling as well