Honestly, I gave up on the racks entirely. I now use the egg carton method. Then, at day 18, I do lay them down. Other folks just leave them in the egg cartons and hatch them upright.
It does seem best to cut a hole on the bottom of each cell for air passage. I just like the cartons better than the racks. The eggs simply aren't uniform enough for the racks to work for me. To each their own experience.