Sweet progress Nick! I've been quietly lurking (and learning) over in the SEOS threads and following along with your build questions. I really, really like the fact you have a curved back speaker similar to B&W's Nautilus line (and Revel, Paradigm, etc.). Did you come up with this cut plan or was that something I missed? Either way your woodworking is really great.
To be honest, I have never seen an instance where someone had baffle panels - only full baffle walls. Procella has a great pdf guide to building baffle walls on their website located here: http://www.procella.citymax.com/f/Procella_System_Design_&_Installation_v2.5_Web.pdf
Baffle wall construction starts on page 19. Generally speaking the more mass on the front of the wall the better, so they recommend one layer of 3/4" MDF glued and screwed, plus two layers of 5/8" drywall with Green Glue dampening between the layers. Then on top of the drywall two layers of 1" Linacoustic (or similar) separated by a layer of 3 mil poly. The "cubbies" for the speakers should be constructed from either one or two layers of 3/4" MDF (with Green Glue if you go the second layer) and be as near-net shape to the speaker as possible. Fill any voids with insulation. To make the boxes removable at a later date, make the box deep enough so the front edges are flush with the double layer of 5/8" drywall and then cover the leading edge with the Linacoustic.
As to speaker height, Procella recommends the "acoustic center" to be at 5/8 up the height of the viewable screen (i.e. just slightly above center). Given the similar design between SEOS and Procella I would imagine your speakers would have a similar "acoustic center".
For the 2pi calculations....I have NFI but am anxious to learn what you find out!!!
By the way, do you mind sharing your parts/material list along with the total cost per completed speaker? I know the SEOS things are like $35, but it is the compression driver and woofer selection that can really drive the cost skyward. Thanks and keep up the great work.
Oh....and I am very glad to see you still have the beers handy during production!!!