I just (yesterday) did my own completely non-scientific version of this. I played with sub placement until it 'sounded better' which I equated to less peaky in the frequency domain. I then recalibrated and my sub volume control is at twice what it was before for the same SPL. My system also sounds better than it ever has. One day I will get around to a proper analysis. BTW I am crossed over at 60Hz.

My Home Theater