Hey Kim, not answering your intial question, but do you do this as Programs in the EP, or as individual emails? I might be the only person who was previously unaware of this limitation, but just learned yesterday that champion/challenger tests can't be run in
any batch campaigns, which includes programs that you put into EP streams.
As for your question, I would really, really, really hope that if it's a single email with a new champion/challenger test attached to it, then the EP would be smart enough to not send to someone who had already received the previous champion.