Let us clarify what we are talking about when you say "Changing Crews" because I'm not sure. Are you talking about changing one person for another person as crew in a two up configuration, or are you talking about sailing Uni vs. two up?
I believe the situation under discussion is:
1, Start event in 2 up mode and then change to single handed
2, Start single handed and then move to 2 up.
Both not on IMO