Well, there were actually only 2 behind you, but I thought about the same thing... basically there were half about half the cards behind you and you'd have filled the bidding with 1... and 2 unknown bids behind you... I still think I'd have bid 1, but I'm fairly aggressive early on... it isn't until I'm protecting a lead that I get really passive in bids.. of course the whole bidding in order is a new wrinkle...
I completely defer to your knowledge here though, because you have probably played a LOT more than I have (only 2 games) given that you own the game.