I did cut my JCP clutch last year because their due date had come and gone and I still hadn't seen any slits. When candled I could see the babies move inside and my impatience just made me cut to check that they were okay.

I prefer to let the babies emerge on their own. I have more experience with corn clutches than pythons and many of the corn breeders I've talked to would prefer that babies unable to leave their own eggs not become part of the gene pool. It may be harsh, but I can see their point and I have never assisted a corn from its egg regardless of how "late" it is.