@daveyf, if you had mentioned in your OP the room treatment in place I would not have been inspired to type a long email trying to be of help.
It seems you to like to jump to conclusions about other people's systems
I did not jump to anything! The fact that I mentioned 2 grey panels should tell you that I obviously had a look at your system, not so? I did not see this as a challenge to 'spot the hidden treatment'
As to why no photos of my system, well I do not feel the need, simple.
I post the photos below, not because of your brash comment but for the benefit of anyone interested in the start of my DIY super-chunk bass traps. They measure 900mm across the width and except for frequency specific helmholtz resonators this is what it takes to deal with the long wavelengths.