Great information as always, easy to understand.

You said:

"Floor bounce is entirely dependent on height. It causes a notch somewhere, usually in the lower midrange, when speakers are placed on stands. That makes a trade-off of competing priorities for two-way speakers."

Is there a desired placement of the four pi's from the floor and back wall that would balance the reinforcing bass level and midrange notch when using them with multiple subwoofers?

I noticed that you usually use risers with the Four Pi's in your application as a stand alone speaker without subs.
But, I have not seen your arrangement of the Four Pi position when you are using them with subs.

"If you add subs and put them a few feet away from the mains, then blend them with a fairly wide overlap, they will smooth each other"
And:
"I would suggest low-passing the subs closest to the mains somewhere around 100Hz and the more distant subs lower, maybe around 50Hz."

Regarding the overlap between the main speakers and the subwoofers closest to the mains.
At what filter slope would you suggest to use here for the main subwoofers, 12db, or higher? Also does the distance of the main subs from the main speakers have any significant bearing on this blending and overlap?

And what filter slope would you suggest for the sub placed further away in the room with the 50Hz crossover point, 12db, or higher, like 24db to 48db?

Thanks

Norris