In retrospect, I appreciate all the advice offed her. I have considered all the advice offered here and I have changed my mind about re-shaping the tang The rear of the barrel is against the sides of the stock where the barrel channel ends. The breech block is against the cut in the mortise. I can remove about 3/16" from the shoulders where the rear of the barrel contacts, and also from the the breech lug cut and it should move far enough rearward to compensate for the error. There is still sufficient room for the lockplate on the side panel of the stock. I/m going with this.