Touch call, Impulse. I imagine you'll probably lose 1 or 2 players before the game gets started (or soon after it starts). That's just the reality of play by post games here at the Inn. Real life gets in the way.
You'll also probably have 2 or so players who can't posted on any given week. (blast you, Real Life!)
I don't know what your idea is for the "main quest", so it may be challenging to scale it for a large group.
My preferences would be for two smaller groups as this seems to be easier to manage as far as dialogue between characters and npcs, battles, etc (less people making decisions makes for quick game play on PbP). It also allows for players to pick races/classes they want without feeling like they are stepping into other player's character's spotlight.
On the other hand, that does mean nearly twice as much work for you... not sure what kind of time you have available. I know you're playing in Schnozzle's game, not sure if you're in some other ones too.
Anyway, thanks for letting me join, and like I said in my PM, I'm fine with stepping aside too. Maybe this is just a sign that more of us need to step up and DM.
Peace,
Ayrn