I got my 36 Tula ex-PE all put together and put a few rounds through it to sight it in. It seems that the rifle shoots very high. With the crosshairs positioned as high as they will go, I'm getting nice tight groups about four inches above the bull using a six o'clock hold. The mount is totally flat on the receiver and I'm not sure how to bring the groups down. Do I have to shim under one of the rings or is there a better way to bring the shots down? Any advice would be greatly appreciated.