From the Q&A...:

"Is it possible to create mono subs with a digital and analogue subwoofer? If not currently available, can a software upgrade be made to do
so?

Meridian Response:
Bob would like clarification on this question please. He will be happy to answer it if possible, but we couldn't come to a consensus on the actual question."

Clarification:

If you have matching subs you can have them Left and Right Sub. With non-matching subs (like one analogue and one digital) you will get one front centre sub and one rear center sub. Kind of a front-rear stereo laugh

There are different situations, but if you for instance set all speakers to small the front centre sub will play bass from front + centre speaker & also LFE. The rear sub will play bass from the rear speakers + LFE.

But, if you have a "difficult room" and are using two subs for more even bass on the different sitting positions, it's better if the two subs play exactly the same sound material. So an option for sending all managed bass to both subs would be valuable. All bass, both front + rear + LFE, to both subs.

HD621, G98DH, G68ADV, Bc Acoustiqe ACT A3, 5200C DSP33, NuForce Reference 9 monoblocks, 2x SB3's, Velodyne DD-15 & DD-12 Subwoofers and a Meridian sub.