You only need two 1/2" holes per 2'x2' incubator. Be careful with the humidity too high. I used to keep the level at over 50% saturation until I started getting curled toes and splayed legs. I've let it dry out completely for a couple days at a time and have never had a deformity yet. Sponges only work if they are real sponges from the ocean with all the sand and salt removed. Grocery store/ synthetic sponges are not a good idea. Shallow pan or the bottom of a cup that you cut so that it will be shallow enough are the best ideas for humidity. Remember, you are trying to mimick natural humidity here. Chicks will hatch with near zero humidity, some agree that this will create almost all roosters, though it hasn't been proven. I have had excellent results with up and down moisture levels in my incubator with a 6 to 1 hen ratio. Golden buffs, gold laced Wyandottes, Red Rocks, White Rocks and Banties have all been well hatched and are good egg layers from my incubator