I'm a novice and know very little. I do know from physics that the rear sight will need to be lowered for well-aimed shots to move down on the target, and the rear sight must be raised for the shots to land higher on the target. I don't know how to make that change happen, though.
Essentially the rear sight must move in the same direction that the shots need to be moved. This is all assuming, of course, that everything in your technique is without flaw.
And let me end this advice with a clear statement: I know nothing more than what I've read in books and on the 'net. My advice is worth exactly what you paid for it.
Buona fortuna, il mio amico. (Good luck, my friend)