Filling Throttle Plate Holes

In another thread, I mentioned that I got a little better idle by temporarily plugging the holes that I had drilled in my primary throttle blades, and cracking open the secondary blades instead.

Now, how do I permanently fill the holes? Do I remember a soldering method? It obviously has to be dependable. New plates?

A small oval head machine screw and nut works well.
Just peen the end of the screw down so it doesn't come loose and fall down in the motor.