Shoot the gun into paper at a measured 16 yds. One barrel only five (5) shells into the same spot without aiming; mount and shoot.
That will tell you actually where your center is with the current stocking. If you want to experiment use blue insulation foam and makes spacers and tape them on to the stock with wide masking (painters) tape. Shoot the paper again at 16 yds. At that point you will know what various height mods will get you. Then go to a really compentatnt shotgun stock guy and talk to him.
