When i recived my new housing i noticed the hole aready had a slight indication of a hairline crack on the edge of the hole. probably caused from the casting process It was very very small that most people wouldnt even noticed it but i recon it would have eventually cracked through like they normally do By releiving the hole and the edge it was removed leaving a nice smooth, formed hole. Its no guarantee it wont eventually crack but it should definatly help the dreaded cracking