I would not incubate the smaller egg. It can cause deformities in the developing bird, because their is not enough space in it. Don't go by air sack size, because that only indicates the age of the egg. The older the larger. Let the eggs sit on your kitchen table for 4 hours so the yolk can settle. When you put them into the incubator avoid the corners and the center of the machine. The corners get less heat and air circulation and the center gets the fan blowing directly onto the eggs. The machine is large, so you can avoid those spots. You may need to clean really dirty eggs just a little bit. Here is what to watch out for: Use water that is 100 degrees so the will be no bacteria pulled into the egg. Do not rub, so you do not remove the bloom on the egg. I use a paper towel soaked in the water, wrap the egg for a few second and simply wipe the dirt off without rubbing. Then I just dry the egg with another towel. Do not turn on the turner once you put the egg into the machine. Wait 24 hours before turning the turner on. Mist the eggs with 120 degree water daily once the turner is on.