The electret elements in CPC catalogue all seem to quote 120db as the max SPL. I would have thought that was unlikely to be overloaded - it's not far from the pain threshold.

We've had no major problems with feedback using Microvox. Our melodeon player sometimes causes problems by putting the melodeon down in front of the foldback, but you can't blame Microvox for that.

Ignoring the polar patterns of the mics, the closer a mic is to the sound source, the lower the gain needed and the less the likelihood of feedback. Microvox gets the treble elements reasonably close to the reeds.