Boy, did that fourth factory slot pay off early...on just the second time I used it I have my first 5* being constructed in it. Actually, I'm really pleased with my luck so far in this game. I've built both the Tiger sisters and found a 5* Emblem of Hope during one of my very first scouting attempts. Nothing outstanding, but still, my army is all at least 4* except for three remaining 3*s...and that's only because I don't use arty units.