When cutting, I wait until the majority of a clutch has pipped, then make a tiny slit in the eggs of the stragglers as a 'just in case' kinda thing. That way, if something goes wrong, they have an air supply, and I can play it by ear from there. Breaching the shell has to potential to be serious. Usually it's not and everything is fine, but every once in a while, something icky gets in. Not gonna lie, when curious, I candle with an older style flashlight. Depending on what you're working with, you can totally identify what morph a late-term BP fetus is through the shell. It seems like I've started making out pattern ~Day 35ish. (Please note that candling is as unnatural as cutting and will stress babies.)

Last year I didn't cut at all and was happy I didn't --- it seemed more rewarding somehow to watch everybody pip on their own.

As a side note, it's seemed so far that the babies that pip on their own are quicker to feed over-all than the babies whose eggs I've cut.