Not sure what size holes I drilled it was about 10 years ago. But they were not very large just big enough to let water drain and not let pieces fall through.
I use these attached to 4x4 post used for pens. One on each side of post, one with grit one with OC. I just drilled holes in bottom to drain, have had them for 10 years now work great for me.
I would not make a safety hole until they have internally pipped. Making a hole too soon aids in membrane drying out. Being patient is your best option at this point.
:welcome Sorry to hear all your troubles if that is your egg in pic that is on day 24, it is very underdeveloped and doesn't look right from picture and not likely it will be a successful hatch. If all your eggs look like this at day 24 of incubation it doesn't look good for any hatching.