I am sorry the water trick didn't work for you.
with my 3 sportsmans, it worked every time.
If I saw the temperature start to climb, I just added water and it stabilized again.
I had 8 hova bators and the water trick worked in them also..
just a thought: if your temperature is lower at the bottom of the incubator, maybe it is because there is water/moisture down there and it is evaporating. whenever water evaporates it cools..
I would not worry about the temperature differences as long as the temperature around the eggs is 99.5 or so..
The temp at the bottom where my thermometer is, is steady at 101°. I worry that the temp at the top of the eggs will be too high for proper development. I'd hate to risk an egg. I'm hoping to get Temps where they are supposed to be without having to do any more effort than the normal stuff. If all else fails, I can manually adjust the temp, but hopefully not on a brand new incubator.