The shim should fix your elevation issue. You could get the UM shim or make your own out of some card stock or cut a couple strips out of a pop can to make a shim. If you make your own put it under the front of the optic.I mounted a red dot on an American Compact 9 mm. When I was zeroing it in I maxed out the elevation and it still shoots slightly low. Does anyone know if the UM Tactical shim will fix this issue?