Build something to mount the atmos to it overhead then. Don't bother with upfiring at all. I've only seen negative reviews and comments about this.
Two of those shelving units you showed and put a board between the two and put the in ceiling speakers there. Also ensure it's framed well enough for it to not sag. It's like building a ceiling below the ceiling.
What's preventing you from putting g speakers I the proper placements eg in ceiling or on ceiling?
Don't give us the crap excuse that you can't when in actual fact you can. It's either you or something else that "unwilling" to do so.
I discovered how to turn your 5.1.2 upfiring Atmos into a virtual 11.1.6 speakers/sound stage.
Meaning if you only have 5 surround speakers and 2 atmos upfiring speakers, it will sound like a 11.1.6 config, you will be hearing 11 speakers and 6 atmos sound stage. The requirement is that you only have 2 upfiring atmos front speakers only. I will be posting a youtube tutorial soon. I would say this is how to correctly set up the original 5.1.2 dolby atmos upfiring speakers. If you can't wait for the youtube tutorial, I can teach you how.
I will teach you the misconception about 5.1.2 upfiring dolby atmos and the principles you need to apply when setting up your 5.1.2 dolby atmos correctly and to experience it like a 11.1.6 atmos without additional speakers.
This sounds impossible, but I just had this setup in my theater and It just sound amazing! it's like having 11.1.6 dolby atmos in my home theater with just a 5.2.2 speakers (1 have 2 subs). You have to hear it to believe it. After trying dolby atmos 5.1.2 uprfiring from 2016 to 2022 and almost giving up on it, I've finally cracked the code of 5.1.2 dolby atmos correct setup.
This principle will also upmix 5.1 dolby surround into a virtual dolby atmos.