Probe Thermostat

I am a mini-fridge in an incubator and I'm just curious where I should place the probe of the thermostat inside the incubator .... measurements are 30 inches high 18 inches deep and 18 cm wide. Also when I add the thermometer should be placed only prob straight in the same place as the thermostat probe.

Thank you

just put about 3 inches below the surface of the vermiculite. sinuses should be the deepest eggs should go,