Since my original post starting this thread, I am getting
some pretty pleasing results with 3 and even 4 mic positions from MIR
Pro. Dietz was indeed right about mixing the mutiple dry signals, so
take care of activating "wet only" in the extra MIR instances. Mostly I
take the dry signal from the conductor's or 7th row (or equivalent)
position, the others all "wet only". One trick that allows me to blend
the wet signals from different mic positions, or even different venues,
without muddying up the mixed reverb signal, is tweaking some delay
plug-ins, one for each "wet only" MIR. In fact this is close to the
underlying idea of what Deutsche Grammohphon was doing with its
legendary 3D and 4D CD recordings, sliding the multiple mic signals in
time to optmize for clarity and localisation.
Karel warned for added latency using this approach. There's indeed some added latency, but nowhere near unworkable territory, at least for me, I am no drummer though, but I can still happily play Rachmaninov in a mutli-miced hall without latency issues. By the way, if you run your close staging the way you run a single VEpro+MIRpro instance and on top of that also output the instruments' (un-MIR-ed) direct signals to the DAW (not the MIR dry signals!), then you can bus those instrument signals from the DAW to the extra MIRs, in which case only those extra MIRs would have added latency in relation to the instruments' signals , which you can then incorporate again in the timing settings for the delay plug-ins mentioned above.