There is a squashing effect between the speakers, I think. The D'Appolito design with the tweeter between two mid woofers squeezes the dispersion of the tweeter between them.However, in the case of a set of domes in a long line very close together, I'm not sure what that would do. Surely the ones on the ends, and maybe the last two on the ends, would have a normal at least quarter spherical dispersion giving more vertical.
But I don't know. Hopefully Jim or Bill F-M or someone here with more acoustics knowledge can reply.
Marlboro