Oh I like that! I have yellow plastic trays I use to hatch in for the same reason, and when I overflow them I put the eggs in the bottom half of egg cartons. I don't know if 3 days or 5 makes a difference, but after 5 days most air cells have settled. The other thing I've read is not to move them on day 4, there is something about the development process on that particular day that makes them more sensitive to handling.