Dolby does not allow in-ceiling Atmos and in-ceiling surrounds. The surrounds are all supposed to be at 1/2 ceiling height, or below. Of course, you can go ahead an do it anyway, but you might find it to be an unsatisfying experience.
https://www.dolby.com/us/en/speaker-setup-guides/index.html
https://www.dolby.com/us/en/speaker-setup-guides/index.html