The 18' wall opposite and it's 7' return towards the wall you see will be covered with the stuff. I'll put pine 1x2 between the panels to break up the monotony. My good friend Larry from Hollywood Sound has had his listening room done like that for years. It will give me a live-end and a not-so-live-end (as opposed to a dead-end).
I've tried things like Sonex panels in the past but never sprang for things like room tunes or traps.
BTW, the toe-in I'm using is occasionally quite directional but mostly floats a soundstage from wall-to-wall on Analog, and only on Analog.