I'm starting a hatch for my first grade class in a styrofoam hova bator. I used this one last year and only got 2/18. A lot of my problems were likely due to not finding out about the last 3 days of lockdown until after (I felt terrible!). There are vent holes in the top and bottom. Not sure how many of the holes should be open (there are plugs to plug them) or closed. I'm also wondering if putting a towel under it would be bad - are the bottom holes supposed to be for air to come in? Thanks!