I havent read thru this whole thread, but Im all over a drier hatch. I have a Genesis Hova that I put my eggs in for the first 18 days, and then put them in a Hova 1602 for the last couple of days to hatch. I dont monitor the Genesis very closely, and only add water now and again...I dont have a hygrometer in it. This past week I had a hatch, and monitored my 1602 closely. Had a good hatch; kept the humidity to about 50. Well, I decided Id better add some water to the Genesis, since Id been ignoring it because of the hatch, and had it full of eggs for future hatches. I opened the top, and there was 6 babies looking at me...I had failed to remove all the eggs that were due. Every single one I left behind hatched perfectly.
So I dont worry about humidity too much any more.