There is a screw, that goes through both parts, in the tab area. This screw needs to hold both pieces securely, so the extension does not move under the safety tab. I did not talk about the safety tab before. This gun uses an upper tang sliding safety. The safety button, with extention, can be seen it the first picture. The tab, or extension, simply slides over the top of the trigger extension so that the trigger can not be pulled out of the sear.
So the placement of the screw is important. One must be able to remove it to dissemble the gun. The oval hole in the center of trigger extention is the path the trigger spring and main spring go through when the gun is assembled.
Holding this assembly together for drilling and tapping the hole is tough because of its odd shape.
This first picture is a crude setup for holding the assembly but it worked well. Machining into a chunk of aluminum was quick and easy.
Picture 2 and 3 are the top and bottom views after getting the screw in place.
Picture 4 prove with the screw in place, with a nice tight fit and rough shaping.
Next to get it working in the frame!
Bob