Can someone confirm that the latest version does efficiently handle channel coupling?

Yes it does. Our wiki was updated to reflect this change. I am trying to get the name of the developer who coupled the channels in the source code so we can give credit were it's due. If you remember correctly channel coupling was difficult to tune due to point stereo with -q values below 6. I am also wondering not only who added coupling to the encoder, but who had the time to meticulously tune it as you need at least a 5.1 setup. Test it and let us know how efficient it is and how it sounds.