That will be a large improvement over the "strips" approach. I'd go further still however, as I don't like any larger unbraced sections. Accordingly you can increase the length of the braces, such that they couple to a third and even fourth panel. Ideal is a funny word, but the concept should be to couple as much of each panel to as many other, particularly opposite-side, panels as possible. There's a balance of material, weight, etc, but to the extent you can, bracing that follows the pathlength and braces it all along the way is generally preferred. So turn your multiple braces that follow the path into the closest thing you can to following the truncated horn spiral, minimizing any length that's unbraced. You can also space them slightly off-center to distribute any resonances across frequency, both panel and internal acoustic resonances. I'd definitely want a strip on the driver mounting section, in between drivers, coupling to the opposite wall in the first section of horn.
you mean here?
also what about double baffle, as being a dual driver design the forces are greater than on a single driver baffle
yes- even if 1.5" thick, that piece will allow for a lot more flexing than you want, so definitely reinforce that section between cutouts (as you are showing).
Yeah, need to factor in material MOE such as it takes a 1.58" thickness MDF to match 3/4" thick marine grade plywood, so when dado for interlocking/bracing, especially if there's significant loss of panel material due to holes, etc.........
Connect multiple panels together to take advantage of the support and structure those multidimensional shapes create. Not unlike I beams and Box columns instead of flat plate steel without a shape or support structures at moments, etc
The best bracing is that which ties two opposing panels together at or near their centers. That last image looks pretty good.