My question is, if you're running 2 sources DFC, what's better: 2 sets of mics one atop another with a clamp, or something like a Sabra-Som ST4 Stereo Bar?
If the latter what would you run? Outside split with 2nd set in the middle, or 2 sets - left and right on same plane?
I don't know if its better or not but I go above
I look at it like this, if you have something between the mics its similar to have a jdisc or your head. It's going to create a different sound.
I could be totally wrong though
I couldn't wait to ditch my Sabra Som bar. I used it to do exactly what you are describing, but it's bulky, takes up a lot of room in my gear bag and is awkward to set-up. When I got my AKG actives I said bye bye to the Sabra Som. This is what I'm using for my full bodied mics now: http://taperssection.com/index.php?topic=164894.0
I don't know the answer to your question, but I tend to think that above and below is better than lining up four mics side by side...
I'm sure someone will chime in with a logical reason to do one or the other.
No strong opinion one way or the other, except if your mics are full bodied mics, putting them in the same horizontal plane can be a PITA if the cables all come out the back of the bar at or close to the same place, so risers and such are handy for cable management.
Otherwise, I don't have any compelling reason to offer why one pair should be aligned in any particular way with respect to the other.