What works is to increase the humidity before hatching begins. If moisture was not a necessary ingredient to getting born, then human and other fetuses would not be nurtured in an amniotic fluid sack that ruptures when birth begins, in effect greasing the skids to help us to easily find our way into this world.
An egg is in effect a chickens' womb. In a cabinet type forced air incubator like a GQF, humidity was never a problem for me. Perhaps this is because of the greater air volume and adjustable multi level air vents but then again I am not a fertile chicken egg so what do I know. Relative humidity of 90% is not too much humidity when eggs start hatching. In a plastic incubator i would think that humidity is hard to maintain because the incubator body looses more heat to the air creating cold spots, resulting in water condensing on the inside. And remember that the wet bulb reading will be lower in a forced air incubator just like a breeze from a ceiling fan feels cold when you come out of of a hot shower because of increased evaporation cooling.
The reason imho that the GQF has 3 incubation trays is so you can set a new tray of eggs each week and then move the oldest tray too the bottom hatching, or non-turning tray on day 18. If this is expected to work with an incubator full of chicken eggs, i don't see why it won't work with a mix of quail and hen eggs.
