BrownEggFan, I too made my own incubator and had trouble regulating temps after placing the heat shield right before lockdown -- so much so that I ended up removing the heat shield out of fear of killing the entire batch. All of my "equipment" was at one end of the incubator: the PC fan in one corner, blowing across the bulb toward the thermostat. The 3 eggs that were directly in front of the bulb did not hatch, whereas all but one of the others did (I set 12 eggs total). Like you, I had been rotating the position of eggs in the incubator so none would be sitting directly in front of the bulb too long. But after lockdown I didn't touch them, and that must have done them in. Good luck getting your temps steady with the heat shield in place. It's definitely what I'll be working on for next time.