I use the cardboard carton bottoms to hatch as I find that they DO absorb some moisture that makes it easier on the chicks to hatch. I put the carton bottoms in the day before lockdown, and lightly mist them as I want the humidity about 60% at least for hatching these very thick eggs. Use a new carton bottom for each hatch.This is, indeed, interesting. Although our hatches are typically strong. I find that in the incubators I always have some chicks stuck in the sell that I'm certain otherwie would hve hatched had they been underneath hens.