If you actually clip it into the sound hole does it not get incredibly boomy and get a lot of feedback? Even with the mic away from the soundhole (as I have it currently) it is very heavy on the bass. Cutting quite a lot of the bass out also seems to help on the feedback side of things

I can remember donkeys years ago sticking a tape recorder mic inside my guitar and it made some very odd noises and some great shrieking feedback!

I'm going to experiment a bit more over the next couple of evenings comparing the sound that comes out of the guitar with what comes out of it amplified and compare it with the Fishman Neo-D pick up I have to see which one sounds better to my ears