I'd say if you're within "thousandths" AND the entire perimeter is still proud of the butt AND the depth of abrasive scratching isn't deeper than the amount required to polish the plastic base and fine sand the pad, you're better than I am. I have a homemade grinding jig mainly for swinging the toe to the correct angle and I do ALL the shaping and fairing off the gun on a staionary belt sander. When I've got down to that chalk or white paint-filled scribe line, I check it and correct and then polish. I don't care if it's a 32nd proud if the stock finish is intact, the lines of the pad continue the lines of the stock, the scratch pattern on the pad is light and uniform, the plastic base is fine sanded or polished to a likewise uniform look.
jack
