I get extremely excellent hatches, close to 100% using a cheap still air LG, the trick is setting it and forgetting it. A mother hen does not have perfect humidity, and does not have a constant temp, she doesn't even turn the eggs evenly like a incubator. Set your temp before loading the bator at 100F for the warmest part of the day, use bricks, rocks or water bottles in the bator to simulate a loaded bator. Once your bator is set leave it alone, it will not hurt for the eggs to drop a few degrees of a night. You can cover the bator of a night with towels to help hold heat, but I never bothered. I even had one hatch drop to 88F in a power outage and still had a almost perfect hatch.