It would not be difficult to make an on-ear/over ear variation on this which I would have interest in. In my experience a flat plate coupling works the best for production testing. The IEC/etc. couplers just add confusion when all you are looking at is differences in production. The MEMs mikes are great since they have very consistant sensitivity and response.
Yes, I think a tweak on this to support over-the-ear would be pretty straightforward. I’ll let you know when we kick that off.