Ta-da, ta-da! I have reshaped the factory grip of my AW93. More volume. The thumb rest parallel to the bore. No more empty spaces under my palm. The center line of the bore lays about 1mm lower than before (or 5-6mm lower comparing to the new factory grip). Unfortunately, after dismounting the rear sight carriage and seeing what we have under I had to say goodbye to the idea of lowering the barrel for another 2mm. There is no place for metal plug (more info about this idea here). The space below the rear sight carriage is fully used by the slide in its most rear position.
From Feinwerkbau AW93