lilmike, you're pretty quick with sketchup! That I'm still learning. (Folding is excellent practice!) I toiled for a couple months trying to fold already-modeled/built horns into a triangular shape that would stack into this same corner, with no joy.
I'd planned to leave an access hole for servicing in the rear cover, by adding a frame around the hole, like the access cover on your F-20. I'm not the slightest bit concerned with looking like a "scoop" cabinet, (we had an old "Earthquake" cabinet that I was happy to see go... maybe 4 of them would have done something, but 1 sure didn't. Sold it with a repaired rubber surround for $300,) nor from deviating from your original, elegantly simple 1-sheet design. These will be stacked 2 wide, 2 high, and will look like a wall with a hole in the middle, (where the 4 side-firing mouths are clustered.) These will actually cover up part of a mirrored wall our patrons seem to like to dance in front of, so we, (the club owner and I,) even talked about covering the surface with plexiglas mirrors for fun. They can watch their pants flap in the breeze!
I've had an ongoing discussion with a couple sales people at Fi, and it seems tapped horns are foreign territory to them. Very helpful with answers about their products though. There is a bandpass cooling option offered for the X10, and probably the rest of their line, that uses some sort of heatsink that attaches to the pole piece, partially covering the vent hole, but conducting heat out of the motor, where scant airflow, (inside the inner chamber of a bandpass enclosure,) has a better chance of transferring it away. Seems this ($25) option wouldn't be necessary with the motor on the "breezy" side of the T-6 horn. They said this piece can be added at a later time, such as when it's re-coned. "To Go", the re-cone kit goes for $60 for this driver.
What say you to cooling fins lilmike? (IMO, seems like $25/cabinet would be better spent on mirrors.)