As someone who has recorded a lot of ambience I prefer to adhere to the KISS principle, which I am sure I don't need to explain.
Off the bat, I anticipate issues using a directional cardioid in an external location - particularly with wind. You will need to ensure adequate wind-protection if you insist on using this type of mic pattern. Anything other than omnidirectional patterns will be susceptible to wind-induced blow-out.
Having said that, you have your reasons for wanting to use directional mics. Just make sure you have adequate wind-protection or your ambiences will not be usable.
Also be aware that the rigs you are proposing will inhibit the workings of the capsule vents, which are the actual mechanism by which the capsules are able to achieve directionality. Any part of the rig which covers the vent holes will force the capsule back towards omni-directionality, but as these capsules are not equalised for omni-directional use you will find yourself with a strange spectral response and not the desired directional pattern.
I would treat a lot of the article you have quoted with a grain of salt. If anyone attempted to suggest to me that a spaced pair of microphones exhibited excellent phase coherence and good mono-compatibility I would back away slowly and when at a safe distance, start running.
Best place to start with ambient sound recording is a simple pair of spaced omnidirectional microphones. You are not looking for good phase coherence or mono-compatibility. This is an exercise in recording in stereo.