Regarding the groups, when Crimmy and I are talking about them, we are referring to the naturally tendency of players to group up. Both of us have a lot of experience in an off site game where there's like 40 players, most of whom control multiple characters, so dealing with large groups isn't too difficult. 

But yeah, none of the groups would be [i]solid[/i] so to speak but rather a case of almost right place right time. Some of them will be more naturally as characters gravitate to one another, and some will more random as the circumstances of the event mean a couple people just happen to be in the same area. 

Long story short, I wouldn't worry about the size of the game impeding our ability to GM or making the game flow less smoothly. Trust me, we've dealt with larger.