You may consider intermodulation (including Doppler) also. That would ask for a real three way, means not a 'sub', x/over ~ 250..350Hz, the classic 'tower'. E/g the Wharfdale are very successful with Linton and such, IM lowered by a factor of 10dB and more. A smaller midrange would help with bringing the center to center distance to the waveguide down, which would emphasize your unique selling point of a best-ever vertical dispersion.
Btw.: I recently raised the topic of 'lobing' in the vertical, and I was told, never mind, shut it down. Now people praise a solution to a non-problem. That's pretty much inconsistent, except ...