Respectfully disagree. I just put in a reference disc and I figured it out. I’m off 2-3 degrees. And I know why. I have new seats coming. 2 of my 3 are already gone. The last one the reclining function doesn’t work. My rear overheads are 100%. It’s the fronts that are off. Your statement may be true for your room, but mine is 15X13. I’m damn glad I mounted mine on brackets to the ceiling now as they can be adjusted and dialed in. The angle is just off, that’s it. And that’s because I’m sitting upright instead of reclined. I just listened to a great Atmos soundtrack and there was some sound on the right channel, right front overhead, panning to the surround right, rear right, and rear overhead right and it was damn close.If you cannot mount them on the ceiling in the overhead positions, then you should have installed them on the side walls for better separation from the front wall speakers. I've found that front and rear heights just make the sound stage seem taller, but without the sensation of the audio coming from above you since, well, it isn't.
Front and rear overheads are Dolby Atmos spec, but Dolby is particular on the angles. I get that now and understand. I’m close. I need my new seats stat!