I trust Perry on the structural side of things like this. If he says you literally can't do it, you probably can't. I'm pretty much in the camp of I won't do it. Too many moving parts and too much to go wrong to trust that I'll come out the other side with my databases intact. No, I'd build the system and then move my databases. It may be more work, but it's safer, and which is more important for the business?