Dave, does the Sierra-2 design work just as well as a center speaker? I assume the tweeter would be rotated 90 degrees relative to its orientation in the mains (as with the horizon).
Is the more limited vertical dispersion noticeable compared to the Sierra-1 if the center is not aimed at listening height? On the positive side, it would help with floor/ceiling reflections that can be problematic for center speakers that are typically below the screen. Given that the horizontal dispersion is so wide with the Sierra-2, I assume the soundstage would blend seamlessly across the front three speakers. Have you done much listening with an LCR or 5 channel Sierra-2 setup?
Thanks for all the details! Can't wait!