Sounds good to me. Being legacy, I'm not affected by any of this but I have one comment and one question.
The comment: premium also includes the "past members" list.
The question: how will you determine the number of group members? Ours, for example, is in a constant state of flux. What if somebody creates a group with 400 members, and immediately afterwards they add one? And then the next week, or month, they go back down again? Just curious.
Messages are the sole opinion of the author, especially the fishy ones.