Heathen, thanks for the MSMW. Sounds good (dig those guys). And very cool that you were able to manage a 7' spacing on the omnis.
Here's a clip of the raw CA14 and AT4031 files: https://we.tl/GGNxlvRxY6
Thanks for that. It's helpful to hear each part in isolation. Here's something which I think will make things even better.
Are you one who does any EQ? No problem if not. This is a big topic in general, and even more so with regards to the potential application to OMT where each part can be EQ'd separately and/or the resulting combination can be EQ'd as well. In general, its a good approach to EQ the center pair and omni pair separately to each sound as good as possible on their own prior to combining them.
But there is an important exception to that, which can be useful to do even if you don't really care to make the effort to EQ the two parts separately. It's this- Often it helps to clean the sound up greatly by reducing the low frequency content of the center pair. Let the omnis provide the majority of the low and upper bass content. Its okay, even good, if the center pair is more-focused on the midrange (especially) and high frequency content. Directional mics with weak bass response (like those more intended for speech pickup) can actually work well as center pair because of this, since their response is sort of pre-EQ'd that way already and fits the roll. Otherwise it helps to use a gentle roll off from the below the upper mids to reduce any excess "thickness" and boom in the center pair. And although I've not tried it, a high pass filter could work for this, especially if you can set the slope to first-order (-6dB per octave).
This represents another aspect of the "division of labor" sort of thing described in the previous post, letting the omnis do their thing down low without conflict.
And a midrange focus in the center pair plays nicely against the tendency of omnis to be less forward in that range. Again, the mic patterns used sort of naturally do this for you, but you can emphasize the trend somewhat with EQ if you want to play with it, just keep the difference moderate.
At higher frequencies I find the interaction between the omnis and center pair to be productive. No need to reduce one to let the other "breathe" sufficiently. Probably partly because the signals are sufficiently decorrelated at high frequencies (short-wavelengths) so the content is different enough, and partly due to how we perceive phase differently at high frequencies, where randomized phase tends to sound "airy" and "open".
TLDR- reduce any tendency toward "mud" or excess "thickness" in the center pair via mic selection or EQ, even erring toward what would be an "over-thin" bass-weak sound when the center pair is listened to in isolation.