2 omni microphones for Left, Right and an out of phase omni mic for noise, bad acoustics canceling

It works. Signal path: Beyer M55 to L input, Beyer M55 to R input, out of phase Beyer M55 to (L+R ie Mono input) - UHER Mix 700 Stereo Mixer ie Adder - Sennheiser HD-580. Alernatively hybrid transformer(s) can be used connected directly to the microphones. The great trick found in (Microphones - Lou Burroughs) book can even be used for a binaural or stereo recording.