Thanks for the feedback guys. The room is an awkward shape for speaker placement as you can see. While the outline is to scale, there are three lots of double doors as well as windows to two sides, which restricts options. This is a project I started while my wife was away looking after her mum who was having a hip operation, which is just as well as the room was in turmoil for the best part of a week, and I couldn't possibly have managed it while my wife was around.
I had not even told her about the ceiling speakers, but the ceiling already has inset lights and heating and AC vents, so it shouldn't have been a big deal. What was a big deal was fitting them. I'm in my 70s and while reasonably fit, even finding the speaker holes from above turned out to be difficult, and climbing over the AC ducting was terrifying. We have lightweight roofs in NZ because of the earthquakes, which means a big gap between the joists. So I'll be sorry if I can't use those speakers.
Anyway, after reading your suggestions I realised I could easily try them and quickly made a speaker stand out of a photographic light stand. That put the surround speakers equal distance and made an immediate very noticeable improvement. I disconnected the Presence speakers, but I was still not getting anything out of the rear speakers. I tried the other Amp configurations which did get sound from the rear and side speakers, but I don't think it was ATMOS.
I can see the 7.1 + option, but I have not worked out how to force
SP2: SUR.BACK
Is that done from the receiver's front panel? I have not found those options particularly intuitive, and I don't have a spotty teenager to work it out for me. It's getting late here so I'll delve into the user guide again in the morning.
I've read a lot of articles and seen a bunch of YouTube videos about the V6A, and have seen conflicting information regards the seven amplifier channels and nine speaker terminals, but I thought the definitive answer is that the receiver can switch automatically based on the source. Now I am at a loss again and not understanding how it works? From experiments this evening I am strongly inclined to accept Trebdp83's advice to prioritise ear level speakers, because my system is sounding very much better after moving the surround right speaker closer and adjusting the levels. I am just not sure I am hearing 7.1 ATMOS with any of the settings I have tried so far.