Attached is one of 3 conceptual drawings for a pair of 10" drivers in a midhorn (chuckling wryly not permitted during presentation). This variation yields the longest path length of the 3. My concern is with possible effects of narrowing the passage width just after the throat (passage height remains same as throat height).
Convenient here would be a BF-style "W" horn, wherein the throat is divided into 2 narrow & equal passages, without the need to compress the wavefront. I would stack the 10s vertically, in that case. Avoiding copywrite infringement, we move on....