My eggs that got shrink wrapped did not have huge air cells at day 21 they were big, but not huge. The air cells were almost 50% of the egg by day 24 on the shrink wrapped eggs. They were probably 30% of the egg on day 21, but so were the healthy ones. I don't think the shrink wrapping killed them. I think they failed before day 21 and the egg just lost a lot more humidity after demise shrink wrapping the chick. I'm of course making a huge guess on this. I know what you mean by loosing your mind. I was dreaming about chicks hatching half way and stressing myself out like crazy. Strange, my stressing about it didn't change the outcome.
I can't wait to do it again.