So you have a wavelength of 42.5cm and no time-domain information.
If the baseline mic spacing is about 20cm, you should have 180 degrees of
coverage.
With a wider baseline you'll have ambiguity as multiple directions map to the same phase difference, but the resolution will be better.
If the mics are not identical in phase response or if they have a phase response that varies with angle you'll need to calibrate for these effects.