I also found hatch rates improved dramatically by sitting my eggs big end up for their hatch. I use a hovabator with forced air and turning racks. For the hatch, I lower the temp slightly, raise the humidity to 70% and I disconnect the racks from the turning mechanism and sit them on the wire at the bottom with eggs in situ. You can see in my avatar - its an actual photo of one of my hatches. I also find that putting an ordinary (very clean, new) sponge in beside the eggs, saturated to dripping point, helps maintain humidity. It seems to me that once you have the eggs big end up, you can't overdo the humidity within reason. Drying out appears much more dangerous. That said there are some in-shell deaths you can't prevent, often due to problems such as the parents being a bit older for example. Scrupulous hygiene (clean incubator with Virkon S every time you use it, reject eggs with poop or yolk on them) helps too.