Cat, I've experimented in the past and I now hang the probe in the middle of the incubator not touching anything. I've tried the probe in the egg box, in the substrate, etc. I found the temps are most consistent when the probe is outside the boxes just hanging there. One thing to consider though, at the end of the incubation process the eggs warm up. I use containers with 12 holes in them. I tape and cover up 9 of them until day 50, then I open up all 12 air holes to keep the eggs from heating up. I've seen discussions with several opinions and I'm sure you can do it other ways, this just works for me.