I built a styrofoam incubator out of a meat packing box. I used a hotwater heater thermostat. I have found that the closest I can get to 99.5 degrees is a fluctuating range between 97.5 and 100.7 degrees. I can maintain the humidity pretty steady at 47% and may remove some of the material I am using to limit the water surface area in the water tray. Is this fluctuation acceptable? I believe the range is directly related to the sensitivity of the thermostat. Any advice?