In the small amount of playing with stereo mixdown playback of the recordings made at Springfest last month from the latest array I posted pictures of above, I've found turning the center mic into a M/S pair is very useful in combination with the omnis alone, and far less important but still possibly helpful when the sideways facing OCT supercardioids are in play as well.
Perhaps not surprisingly, when only listening to the center M/S pair on it's own, use of a lot more Side-channel in the decode ratio is appropriate. In combination with the spaced omnis, less Side is most appropriate, and in combination with both the omnis and the sideways facing OCT supercards, very little Side component if any works best. In that case, the sideways facing OCT supercards are already contributing plenty of rich near-spaced 'Side' information. However, in all cases I seem to prefer at least a slight touch of Side from the M/S pair, which seems to make the stereo image spread slightly smoother across center and less center detented when the center is mixed in at higher levels. But that might be because I was using a supercard center microphone to maximize direct pickup over ambient pickup in that channel, instead of a cardioid (or even omni) center called for with the OCT technique. If I switched to a cardioid center, or perhaps spaced the side-facing OCT supercards a bit less far apart, I may not need any additional Side from the M/S 8 to "slightly open and unstick" the center.
So I think in terms of practicality, I'd probably choose either OCT + omnis, or M/S + omnis, rather than both, unless it's easy and I have plenty of recording channels to spare. But it's a bit too early for conclusions so the experiment continues.. This weekend at Wanee I'm going to limit the channel count to 6 so I don't need to haul and power the V3, and will probably do that by eliminating the rear facing pair all together. I plan to record the wide-spaced omnis, OCT supercards and center forward-facing M/S pair. This will allow for more listening to combinations of spaced omni and/or OCT and/or M/S center recordings made in a different recording environment- still outside, but recording from further back at the soundboard in a much bigger outdoor stage setup. Also the music is less acoustic Americana stuff and more amplified rock stuff. Likely recording from within the board cage (or immediately adjacent to it), with the board tent and a beer tent immediately behind, so there isn't the same clean rear audience ambiance I'd want to pickup from behind as there is when recording from well FOB in the "excitement zone".
Rocksuitcase- My suggestion in playing with your combination mix is to try bringing up the omnis first, then the center (Mid) 8 in combination with the omnis, and once you get a good level balance between those three, play with adjusting the M/S ratio by bringing the Side 8 into play.