Please, just a word of caution... If you are going to do a whole zip like that, check for active blood vessels by moistening the membrane, and if there are none, then tear the membrane. Leaving it in the incubator zipped like that, it has nothing to press against to enable it to push out. Once you go that far, you have to continue. It would have tried to stretch and stretch and never been able to tear the membrane on its own, because it has nothing behind it.
I appreciate the word of caution. My concern was that the membrane was glued to him. I was hoping being wrapped in a wet paper towel in the incubator would help soften it. Guess not. Do you think the others will have the same issue? I re-raised the humidity before they pipped.
Also, all of the chicks have some matted down from hatching. Do I leave it or try to wash it off?