Are you using these for hatchlings? I would make the smallest holes possible. I use a soldering iron, just the straight, solid kind, and my hatchies will press their noses into those holes and push. I haven't had an escape, but they _will_ try.
For hatchlings in an enclosed rack in shoeboxes (I think 6 quart) I do one row completely across the front and the back, and two more rows in the center- 10, 3, 4.