ok about a month ago I built a bator out of a mini fridge. The temp swings were crazy. 1 rack would be 100 the rack below it mayby 4 inches would be 96. So I fooled around and finally added another light. Now I have 2 100w lights in my bator, 1 top 1 bottom, 2 4in 12vdc computer fans and the temp swing is less than 1/2 degree throughout the complete bator. 1st batch of eggs had a 100% hatch rate, 48 eggs 48 chicks, My wife and kids were amazed.