I am making a small/medium sized incubator and am trying to decide if I should add one 120mm fan at the top, centered at the back, or two 80 mm fans at the top, on the left and right at the back. The heat tape will run down the back wall in the middle. The incubator is approximately 3 feet tall and will hold eight sterilite 6 quart tubs. Is there an obvious benefit to either fan setup or would either option do the job well enough?

Thanks in advance for your thoughts!