Bipoles can work ok in such situations. While not ideal for pinpoint imaging, 5’ would be pretty close and I think hotspotting would be more distracting than a slightly diffused sound.
How high is the ceiling? Imo, 3’ would be too high. While it wouldn’t necessarily kill the Atmos generally speaking, it would definitely change its effectiveness. Atmos is based on angles, so it’s best to follow the guides. Problem is, there are a few of them, and some are contradictory.
What are the overall room dims, and associated gear?