I set them close to what I THOUGHT was the chicks back height and waited awhile and had to lower it a bit but u can lower it easy. Just have to pull a tab on each corner and u can do that from the top by just curling ur fingers under and pulling. I love this thing but i didn't want to spend $30 for a top so i just put a tote lid on top and i can take it off and knock the poo off or rinse it for free !. lol I have 25 chicks brooding right now but i got the biggest one so i should be covered for whatever i hatch.
Good luck with yours
I am going to learn by dead chicks, which sucks, but I don't see any other way. I got 2 large plates to pretty much fill the brooder, so there shouldn't be cold spots, but with the temps being what they are I can't be sure.