I noticed that in most (or all) of the "Surround-to-Stereo downmixes", the surround seemed to always be turned off by default. Yet turning them on along with the Main stereo mics just seems to add a bit more spacious sound of the room, since the surround mics appear to be more used as outriggers capturing a wider overall sound. On your website, it states the following:
"The main surround microphone settings may also be used instead of the main stereo room mics in order to achieve a wider and more ambient mix. Blending surround signals with the other microphone signals creates a denser, more lush overall sound, even in stereo applications."
So was there a specific reason why the surround mics were not included by default in the downmixes? After trying them along with the Main mics, it seems to sound just fine, even when mixing to a stereo format. In fact, the surround mics appear to be just another stereo pair capturing a bit more of the room sound. Based on the setup diagrams, they don't actually appear to be placed in the back of the hall.