Looking for some input on rear speaker placement. There is about a 12-inch shelf between the wall and couch, but its slightly below the couch level. Ear level is about 4ft. The doorway can be closed off, but there is nowhere to mount speaker above it. I feel my only option is to wall mount the One SLs on the wall behind the couch, but not sure on placement or height. I’m thinking each corner of the couch with them tilted downward, but what height would you recommend? FYI System is Beam (Gen2) ONE SLs for surround, and Sub Mini once it arrives. All the AV equipment supports Dolby Atmos.