Sorry, bombarding with a couple more questions...
I see the DIY threads line either the bottom or the back with water bottles, what is their purpose and are they really necessary? And some other incubators don't have water bottles at all?
Also, what are the oxygen needs of the eggs? How many holes do I poke in the 6qt tub holding the eggs? How often should/shouldn't I open the incubator for air circulation or to not disturb them at all?
And... how many cm of water do you use below your egg crate, assuming substrateless? What is the humidity requirement of the eggs?