I have a Geberit in wall carrier that I will soon install. The instructions state that there should be 3/4" inch space between the face of the carrier, which is suppose to be flush with the surface of the studs, and the face of the finished wall. If I don't have tile and am using green drywall or cement board that is 1/2 inch at most where do I come up with the other quarter of an inch? Does it really matter if I back the carrier into the 2x6 space 1/4 of an inch...wouldn't think so!