Not sure.... heat rises..... maybe one at the top and one at the bottom on opposite sides. You can use black electric tape to cover them if needed. WAIT to drill holes till someone else comes along about placement, I am not sure. My bator is not like that.
You need to figure out a way to keep the heat in and get some ventilation. with that bator you might have a hard time keeping temp with ventilation since there is no insulation.
Ok thanks, anyone else? I am hoping to get it all sorted soon so I can hatch some eggs as soon as my chickens start laying frequently