If you don't feel comfortable cutting your eggs, don't do it. Day 55 is pretty safe.

I had one clutch that I felt was doomed this year and cut the eggs at day 36 or 37, so I cut them and they ended up making it full term. One of the babies was in rough shape, but seems to be recovering quickly. I had to check them daily to make sure they were staying hydrated and to wipe away any bacterial build up...so yeah, not something worth making a habit out of.