I have 9.5x12 feets room.
The more I move the speakers back towards the wall, the soundstage gradually becomes flatter but the music doesn't really move back.
The GIK Gridfuser diffuser on the side brings a little touch of ambiance towards me which gives a little less illusion that the sound is stuck between the 2 walls.
If I don't put anything on, it's still very good but the music is a little more stuck.
If I stand up my absorber panel, the music comes quite a bit from just in front and I kind of feel like I need to do something to widen the soundstage behind.
At first, I put my 10 2'x4' (4in) panels in my room.
It was too muffled and I lost the moods of the music unless I listened loud enough.
I only have 4 left in total and I'm in the ideal range for the RT60.
I tried almost all position absorber/diffuser everywhere ...
All is good but if you want a soundstage more than still sound and perfect data, I prefer diffusion/scatter.