I've actually gone with a setup where I used multiple thermometers. One is attached to a thermostat that I use to power my ballast heat source. The 100w reptile lamp is trimmed out so that the incubator runs 99.5*, and is adjustable for swings in ambient temp. I then use two 17w seedling mats to bring in extra heat should the incubator get cold. I initially started with one mat, but found that if the ambient temp dropped 10 degrees, it could not keep up on it's own. So I installed the second, and now find that the temps never drop below 99*. Once the temp reaches 99*, the heat pads turn on, and turn off once the temp reaches 101*.