I can't say it for the top speakers but the front wides are often not used, that's right. I think the 6 top speakers are used if there, only the front wides are the ones not often used. In theory there shouldn't be a fixed channel layout for Atmos, there should just be Atmos and the decoder should decode it to as many channels there are in the setup. It seems that with Atmos at home this is different. Probably also a limitation of bandwidth in the compressed stream. The DSU (Dolby Surround Upmixer) does not do anything with an Atmos signal I think. Only non atmos Dolby signals are upmixed, but only to 7.1.6 max. It doesn't use the front wides either. So front wides are rarely used, but there are definitely Atmos tracks that use them, especially the trailers and test signals I linked in the thread in my signature. Hhowever you don't have to set up extra rooms for 7.1.4. 9.1.6 is all you need for Atmos (if the PRIR contains all those speakers of course). I have only set up a 9.1.6 room and a 5.1 room from the Surrey room. Luckily there are Ls and Rs speakers in the Surrey PRIRs that you can use for 5.1 although they have an azimuth of 135 degrees and are also used as Lb and Rb in other setups. So as backs they are theoretically too far apart and as surrounds in 5.1 too near together, but it's a compromise.