I've got a new Savage Mk II .22 that I mounted a Primary Arms ACSS .22 scope on, the mount was the one that came installed on the Mk II. I've run out of elevation adjustment and am still about 6 inches low at 50 yards and I want it on at 50. I know I should shim the back of the mount but am looking for any advice on how much and what to use for the shim. Any help is appreciated.