You'll need to contact them about that, sorry. Like I said migration is a nightmare and there's no getting around data loss, you will lose some data. I've always installed CB then directly copied over my CB database tables. Once done I exported from _users, used REGEX to mass modify the export file, re-imported my users. Now that the users exist I manually exported and re-imported the usergroups mapping database table. It's a lot of manual database work, but has zero user loss. I don't recommend this approach unless you've very good experience with database usage otherwise please use migration tools and CB Juice.