Here’s a 1st report: 6 OC 703 panels placed at various places.
(a) Placed on first reflection on floor, immediately under ceiling reflection spots. Had noticeable reduction of harsh upper mids and treble. Even better on some tracks with two panels.
(b) Placed along front wall between speakers, mostly, four panels. Vocal tracks which were already located in the center became much more focused. E.g. When before I was listening to “a singer” in front of me, now I was hearing the vocals from “a singer’s head.” So much better localization.
(c) Placed on rear wall -- which is a bookcase with books pulled out at various degrees -- there was very little change I could hear.
So far so good. Didn’t try to measure, just listened.