This stereo rail consists of three 3D-printed parts, two 3/8" screws, 1/4" insert, and a 2020 aluminum profile. It puts the microphone capsules as close as possible together, on a vertical axis, and in a 90° angle to each other. Each mic capsule consists of a front and back membrane. The mics, two Austrian Audio OC818 have two outputs each - one for each membrane. This way, all directions are covered and I can generate all kinds of stereo and surround signals afterwards in my DAW.

All with a portable/luggable setup!