[TotenKopf]

Personally I have to agree with lexantis...
I found out that 4 infected IS something that COOP has to have playing on expert.
It gives real feel about "being surrounded by zombies in enemy territory"...
I have also "tweaked" some settings, so now I have 4 infected on expert which are spawning every 15secs with ability to spawn 3 hunters at once. Basically - you have 2 infected at any given time chasing you (that is how it works - spawns 4, you kill - 1-2, and then while you are trying to take out another 1-2, another 1-2- spawns - AWESOME!)
REALLY HARD and it changes whole concept of the game. I.E. week or so ago - I was playing with my friends COOP "commando"-style - "point and shoot" - basically no tactics. 4 of us were spread very widely. Now yesterday - with this plugin onboard and settings I have describe above - we were forced to stick one to another no further than 2-3 meters. To complete campaign alive - we were moving very slowly defending agains infected specials and waves of infected themselves. Just defending against wave of common's and then slowly moving to another shelter to prepare to defend ourselves against another while constantly chased by specialls...