Anyone else notice that coop gets too easy after 5+ players? I'd be nice if it scaled the spawn rate (and alien types) with the amount of players.

Just set the lives counter to 5. That'll make it harder!

There are a number of things you can do to make it more difficult. Select item respawn time, turn game speed to 100%, disable certain weapons, use a limited number of lives, use shared lives, turn falling damage on, turn friendly fire on (I don't recommend this because of team killers, but w/e).

Yea I normally set it to 25 shared lives, 4 Marines and 2 Preds, and always 100% game speed. Just wish the spawn rate went up as more people joined =\