After reading a hundred posts about leaving the microphone plugged in, I tried, and for some reason, my system works fine with the microphone plugged in.
I am using an extension cord to bring the microphone plug into the cabin. Andy confirmed that it was OK to do so.
On an interesting note, the extension cord alone with no microphone plugged in fools the MS8 into thinking that the microphone is plugged in. I suggest one of you guys try to run a calibration with no microphone this way. The result is very interesting and I'm sure someone like VP would extrapolate a lot about what the MS8 really does from such a test.