I'd place the microphones so that each is approximately 6' to 12' away from, yet more or less directly on-axis with the PA speaker on each side. That's going to wide space the mics significantly, so you'll want to shift them inwards towards the inner edge of the radiation angle from each PA, but make sure the mic placement is still fully within the rather narrow on-axis radiation angle of the speaker. One way to assure that is to make sure you can see fully down into the driver throat of the high-frequency horn as viewed from the mic position on each respective side - that is, each mic "seeing" fully into the horn on it's own side, not the horn of the speaker on the opposite side. I'd then angle the microphones so that they point directly towards center stage (rather than directly at the PA speaker) to maximize their high frequency pickup of any direct sound emanating from the stage. Yes, the mics are omnidirectional, but they will pick up more "acoustic sparkle" if pointed directly at center stage.
The idea behind this is to get a good blend of clean monophonic SDB through the PA, along with sufficient direct sound from the stage, in combination with the right amount of indirect ambient audience reaction and room sound. Placement too close to the PA will make the SBD part so loud it overwhelms everything else, and if there isn't everything represented in the PA, whatever is in there will be overly dominate everything else which isn't. Don't worry about the seemingly quite wide-spaced mic placement, the sound through the PA will be mono or mostly mono and will thus solidly fill the center of the playback image as if the mics were close together. The inwardly pointed angle of both mics facing towards center stage will also help provide sufficient solid center image. Yet the wide spacing will nicely decorrelate the ambient pickup of audience reaction room reverberation.