I did rearrange the treatments in the living room again but hadn't had time to post an update because I was still trying to understand what I had learned.
In principle I didn't change much -- put back the nearer of the two 4" Safe & Sound panels and added a second rigid panel on the windows behind the speakers - but the surprise came once I figured out what I should be listening for when fine-tuning the treatments. Once you get the big things like bass trapping out of the way, the improvements come more in areas like imaging.
Making the most recent set of changes gave me a soundstage that was very evenly spread between and beyond the speakers (one of those "you know it when you hear it" things) but the biggest surprise was that the spatial effect from phasing (I was listening to Heart's Mistral Wind and the first Tubular Bells album) went from minimal to "room filling". In hindsight I'm surprised that I haven't heard anything like that on "demo disks".
That said, more of my time (when I wasn't working, which was about 99% of it) went into things like this:
The 4x8 plywood sheet was fastened to the horizontal 2x4's to make a target frame 200 yards from the top of the hill in my back yard (I live out in the sticks). A one pound reactive target (same idea as Tannerite but made in Canada) was perched on the top of the plywood leaning against the tree, and I was trying out a new rifle (Tikka T3 Lite in .260 Rem) after sighting it in at 100 yards.
First shot, yay. The explosion doesn't look like much with naked eye at 200 yards, but through a 10x scope it fills the field of view and you get an orange-red fireball that you don't see otherwise.
Still trying to make time for the annual boomershoot matches: http://www.boomershoot.org/
And yes, since taking the picture I have cut down the brush behind the target board so I can be sure nobody is standing in it. The firing position is actually up a hill so I'm shooting down into the ground (in fact the ground slopes up past 200 yards), and the brush only extends back about 10 feet so visibility behind the target is much better than it appears from this picture, but don't want to take any chances.
Anyways, I suspect I'm fairly representative of forum members - largely absent during the nice weather but back once the weather turns bleak. What the staff at the skeet club call "a foul weather friend".