I used tinfoil covered cardboard between the light and the eggs, a 25w lightbulb, a 1" hole just above the light bulb covered with duck tape that I could open a little if it started getting a little too warm, and I set the incubator in my bedroom which is only used when I go to bed at night so there's not a ton of doors opening and temp fluxes because of room activity. It stayed pretty much between 99-101 degrees. I did have to put a towel across the lid at night when it started getting colder at night but other than that I didn't really have any issues with the temp after I switched to a 25w bulb. The 40w kept spiking the temp to 104 and even 106 once. yikes!