One way I found of doing a neat job or relieving the back of the forend so it doesn't contact the receiver is to wrap some sandpaper around a twelve gauge shell. It fits about perfectly and relieves that area uniformly across. Doing that to mine was all it needed to shoot well, I've got it so a thin (.003) piece of paper just barely fits between the receiver and the end of the forend. The gap doesn't show at all.
