I have a AA kit for my Glock 20. It too shot a little high and had to be sighted in with the rear sight lowered as far as it would go. But it's fine now.
One thing I have noticed about the Glock sights they use is if you line up the sights so that you can see all of the white dot through the rear sight you are not lining them up right and will shoot high. If you line them up like regular target sights and ignore the whit dot it will shoot to point of aim.
