By using XY on the hypers, there is no phasing. All your phasing is decided by how much omni you add, along with most of your bass response.
Interesting, can you expand on this concept Joe?
I like doing that too for the same reasons, although I personally prefer more space between omnis. I didn't want to go into specifics above, but when running omnis + directionals my thinking goes in two directions:
1) Spaced omnis work on a time-of-arrival basis for stereo. X/Y configs are purely difference in level based stereo with no time-of-arrival differences. Near spaced configurations like ORTF, DIN, NOS, etc. combine the two approaches and are a sort of a practical compromise between the two. Since I'll be combining different configurations myself, I figure I'm likely to have less potential phase problems if one pair is coincident and thus has no phase differences itself. That's purely a practical thing to make mixing easier and more likely to work well. It's one pair being coincident that makes the difference in this case. The choice of weather to use cardioids vs hypers vs fig-8s for he X/Y pair is separate choice based on other considerations.
I also figure it may be more productive to combine the more different approaches to give me more of a chance to optimize things one way or the other. If I have wide openness from the omnis, I don't have to worry as much about the X/Y sounding center heavy and narrow on their own. Some of that might be exactly what the omni recording needs.
Taking that deeper, if you are into messing around with post work, you can play with ways of further emphasizing the influence of the omni pair on the low freqeuncies and the directional pair on the higher frequencies by EQing them differently. Since the directional ability of human hearing becomes more phase based at frequencies below ~700Hz and level-difference based at frequencies above that, choosing configs that optimizes each pair for opposite ends of the hearing range might be useful. You can go yet further down that road by using complementory highpass and lowpass filters that cross-over completely between frequency ranges. That approach should also reduce any phase interactions outside the cross-over reigon significantly, but you need to set up the filters carefully so the transition sounds smooth. If you want to run a near spaced config and the spaced omnis* and find you have phasing problems, that approach should help reduce the phasiness, but it's more complicated than what most tapers want to do. Schoeps makes mic level filters designed to low pass their omnis around 100 Hz to extend the bottom response of their hypers and 8s in combined arrays where each capsule handles its own range without interference from the other.
Sorry to make this over complicated, but mixing multiple channels of mics brings complications, which is partially my point.
Thinking about doing this for a few upcomming shows. ..the omni's would be slightly higher and about 1 inch further apart than the cards ..
2) The other way of going, which to reduces potential phase problems with four mics in near-spaced configurations is to place the omnis and directional mic as close together as possible, so that the different mics are coincident on each side. Usually that means spacing the omnis pretty close to match the near-spacing of the directional mics, which is likely to compromise the omni recording on it’s own, but eliminates phase problems when mixing the two pairs. This works for tweaking frequency balance using the two pairs, and also changes the polar pattern as they are mixed in various combinations.
To connect that idea to another recent thread, one unusual arrangement I think would be very useful for recording from farther back is spaced hypers pointing directly ahead, like spaced omnis (more spacing between them than usual to compensate for no angle). That would maximally reduce all off-axis sound, reverberation and room echo that is usually the main problem from recording from farther back. If a second pair of omnis were arranged coincident with the hypers, you could dial in a balance between more bass extension and ambient room sound (omnis) and less bass and room sound but more direct clarity from the (hypers) without introducing any phasing.
Basically if you are planning to mix the two pairs, and are concerned about phase problems, you either want them as close together or as far apart as practical.