I also do not use GLAD press n seal. Never have. I just use the snap on lids that came with my boxes. My method of substrateless with extra deep hatchrite very well drenched, cross stitch plastic canvas, and then the light diffuser grate, all insure that my humidity is 100%.

Plus my incubator has the heat source coming from below instead of the sides and my egg boxes are above the heat source. This is best to insure that the humidity stays constant in the egg boxes.