I gave it the weekend to be sure it was done then manually ran 'dspace database migrate' again. If returned much quicker but nothing had changed. Of the 5105 author records I expected it found 4817. I guess that's not bad. If I knew a way to tell what it's not finding it might not be too much work to just reentering them by hand. But so far I haven't turned up what is different between the two copies.