I'm Old School and still follow the 5.1 spec for surround channels.
A few feet behind the listener.
3-6? ft above
Across the room (no toe-in, not pointing towards listeners)
I know they are full audio channels and considered more directional now but their use is almost always surround rather than discrete effects. So that's how I set them up.
It just so happens, your setup is perfect for this!
Being too close to the ceiling isn't ideal but it's better than being too low and close to the listeners.