Well, I finally had screamers show up. First as soon as I loaded the game, 2 radiated screams appear and call in reinforcements. Then right before I exited the game, 2 more radiated screamers showed up and called in reinforcements, including another radiated screamer. Maybe it is a bit much now. At least it should only have 1 screamer to begin with and then a chance of another being called. Right now, it starts with 2.
Not a big deal really. I'll have to put up some guns to deal with them. But still a little overkill.