I've always wondered about the lack of ventilation holes in the Incuview, one question the MFG did not answer in that thread AFAIK.It was on fb. He said it allowed co2 to escape and let oxygen to come in. Did 6 1/8 diam holes and then had 100% hatch rate.
But my first hatch with Incuview was 100%, other 2 have been about 80%.
Lots of variables with hatching, including how percentages are calculated.