Depending on the design of the gun, minor adjustments may be made by using a small shim at the juncture of stock and receiver. I use folded aluminum foil. Loosen the stock bolt and place a few layers inside, tighten up and pattern at least 3 rounds. If correct, leave it along, otherwise continue to adjust incrementally. To raise the pattern, place the foil at the bottom. I use 870s,BTW.
Otherwise, a pad on the comb may help, but oft they drift the pattern a bit left or right. If it's close enough, fine.
On a GP wing shotgun, I like the pattern a little high, but not all above POA. Maybe 60-40,like PJR said.