Some good points being raised. I'm looking forward to more and more measurements, experiments with your subs. Again, congrats so far, good lookin' out
I've got many points to make and questions to ask. but first about the room modeling stuff;
Whether it's some free shareware room mode calculator for subwoofers, or Yate's et al Cray supercomputer crunching,....it's only going to be as accurate as the input data. Merely examining modal activity with Height, Width, and Depth, is myopic.
I've found (obviously I'm not the first) that room mode calculating is only a very rough draft of what may, or may not occur. Boundary impedances of the floor, walls, ceiling, etc., ultimately play a heavy role in determining exactly what will occur in our HT's modally. Furniture occupying significant cubic quantity, both impacts PVG onset, but also affect time domain behavior of the subwoofer spectrum.
Not just wall material, however ceiling joist size, spacing, adjacent load sharing vertical stiffening members, doors, headers, you name it,...every conceivable element all sums in a nearly infinite set of variables and forms your acoustic environment. Sure some of these elements weigh more heavily, however the sum of many seemingly insignificant components could easily skew an otherwise intuitive result, into an acoustic environment that's subsequently counter-intuitive.
I mean this effects stick built/woodframe construction perhaps more than a concrete bunker style room. Mine for example; not my mix room, but in my non-dedicated HT space, I've got so many odd ball architectural elements. I've got three pocket doors in the room, which really compromise a walls structural integrity. I've got a ~10' sliding glass door to the outside, a kitchen at the far end, a floor to ceiling brick fireplace along one wall, etc., etc.
My point is the modeling is great, but measurements trump all the conjecture.
So these individuals that have Yates, for example, custom stealth build in a multi-sub install, may be locked into their proposed design. However those of us that actually measure every element
and move the subs and affect the response accordingly, possess the distinct advantage over the mega buck number crunching. Just sayin
Also, I've enjoyed the advantages of a multi-sub rig since the early/mid 90's. I've planned a new multi-sub approach spanning the vertical with both a multi manifold attic IB, and small sealed balancing subs employing selective mode cancellation for a couple years now. Problem is, my cardio-thoracic rig
been falling apart, and it's a bit out of warranty
This has made the attic crawl a real bitch,.... however,...significant progress has been made as of late.