Originally Posted by Cerebrus
... I would like the POA to match the POI
Is it the windage or elevation that is incorrect? Windage is easily corrected by simply drifting the rear sight.
HK pistols are factory zeroed at 25 meters for a "straight on" hold, the front sight should cover the intended target. POI will occur in front of the dot on the front sight. This is already the POA/POI sight alignment your desire.
In addition, there are also six different factory height front sights for the USP that will allow you to alter the factory sight picture.