My incubator is built like a tank. The most she can do is block my viewing window. My first incubator was, however, a favorite of our ferret. As soon as the eggs got that nice developing egg smell he would try non stop to get in at them. He never succeeded, but I still designed this one to resist anything he could possibly throw at it. The walls are so thick and heavily insulated that no matter what you put on top, once the temperature is stable and adjusted for the average ambient air temperature of the season, it doesn't change aside from the normal +/- 0.7 degrees.
I'd like to hear more about your design.