Yep. The more angular separation between the bed layer and height layer the better. Otherwise it’s all on the same plane, and that won’t work. Atmos uses the difference in height to phantom image sounds into the room, and just like LR speakers that are too close together, it won’t work. I’m going by memory, so a pic would sure help my little brain cell! Lol
Iirc you have 3 across the back? The one on the back wall should be removed(Atmos also only works in pairs so a single rear is out) and then just use a 5ch bed. Nothing wrong with that at all. Back when I had 5.3 I had imaging behind me all the time.
Another thing is placement of the modules. Ime you can’t just plop them on your mains and call it good. You MIGHT get lucky, but more than likely you’ll have to experiment by tipping them foreword or backward as your basically making a bank shot like on a pool table. Hoping it hits the ceiling and lands on the couch. Ceiling height is important too. This picture is just to give a kind of idea how placing the modules at different heights vs different ceiling heights can change the effect. It would be simpler to angle them up/down but I haven’t doodled that out yet lol