Danny, could you comment on how this new design would compare to a LS9 mounted horizontally as a center? Specifically regarding the horizontal dispersion.
Completely different!
An LS-9 on its side is not a very ideal center channel.
The tweeter line length is 70.875" long. for it to maintain an even response you need to stay above the first tweeter and below the last one. In other words you have about a 54" range where the response is the same. Above that or below it and the highs start to drop out of it. And if you are outside the length of the tweeter line then there basically is no highs.
So if you laid it on its side you'd basically have to sit right in front of it +/- about 2 feet each way.
The new LS-C has a wide horizontal coverage area just like a standard N3S kit. So you'll have the great off axis response of a narrow (5/8" wide) playing surface element of the Neo 3 pdr. And in this case, the deep back cup Neo 3 pdr.