But for experimental purposes I'd suggest using the U87 in fig-8 mode for the Side mic and either the SM7 or M3 as the centre Mid mic.
All you need to create a mid-side file is allocate the mic mic to channel 1 and the side mic to channel 2, and record as a stereo file.
However, you should also ensure that the in-phase side (front) of the U87 faces to the left of the sound stage (as viewed from behing the mic array looking at the sound sources). You should also set the preamp channel gains to provide a similar sensitivity for both mics.
The easiest way to do that is to decide where you want the nominal left hand edge of the stereo pickup area to be, then get an assistant to stand there making a fairly constant noise (humming, for example). Adjust the gain of the two preamp channels to give roughly equal output from both mics.
Technical Editor, Sound On Sound