Thanks. This really was a premature question. You really have to tinker with it yourself to get desired parameters. Thanks for your tutorial. I used it to set up my hovabator.
It is exceedingly dry here, so I seal up all the holes and fill the channels in the bottom with water. I also use shoe boxes with lids to keep humidity where I want it.
Hovabators and similar type incubators are actually designed for poultry eggs. With poultry when the eggs begin hatching you remove the plugs to provide more oxygen to the newborn chicks. With reptiles the plugs don't serve the same purpose. They can be used more for humidity control than anything else. I would base the ventilation needs on the humidity level that you're trying to maintain within the incubator. If the humidity level constantly gets too high, you may need to remove the plugs. If you're having a hard time maintaining the humidity level the plugs would probably need to be left in place. I actually open each incubator twice a day for just a few seconds to introduce fresh air and allow any possible built up gases to escape.