I would not change Dietz's positionings, because they are very good the way they are. I would change the settings of the microphones.
I think the dry/wet is a bit misleading, because people think (at least I'm guessing here) that this is the relation between the close and the main microphone. It isn't. In MIR Pro it's always a combination of both. The ratio together with the reverb length defines/shapes the room.
For example the overall ratio in the Synchron Stage is approximately 30 % wet and this shoudn't be changed, because this setting resembles the "real wetness" of the instruments. Of course, some instruments need slightly different settings, but if they are once positioned and set, they shouldn't be changed when applying the term "closer mix". In reality, a close microphone has the same wetness as the main microphone, isn't it? The difference between the two is the distance, the panning and the stereo image.
Hope I don't talk nonsense, but this is how I understand MIR Pro now, and it took me a long time to understand this. At least I'm fine with this. ;)
@Dietz:
Comparing the MIRx settings to the Synchron and BBO libraries I stumbled upon the microphone delays. In MIRx the secondary microphone has a wet delay of 12.2 ms. The room microphones in the Synchron Player are set to 21 ms. Wouldn't it make sense to set it to the same value in MIR Pro? I tried and also increased the volume of the secondary microphone from 3 to 4 dB. I don't know... Maybe the value in MIR Pro can't be compared to the real thing. I like this change, and this is the good thing about MIR Pro compared to MIRx.