GRB, great discussion. Also reminded me about something that I had thought about and then dropped: Polishing the surfaces between the front and rear FO sight posts. I AM going to do that the next FO rod change. 
The "depth" of the rear notch discussion was also interesting. .22 rimfire target pistols often have that deep rear notch too.
What's the idea behind the polishing?
A couple of years back I picked up a rear sight for one of my 1911s and is has a very deep notch and is also
.140 wide. It has become my favorite rear sight for those. (10-8 Performance Nat'l Match)
Another thing I've been playing with recently is the rear notch being machined at a slight angle (front to rear) so the very front of the rear notch is .020"-.030" lower than the rear. This gives me a very crisp edge and I don't pick up any glare by looking down a "tunnel". I've got about 10 rear sight blanks in my tool box right now, trying different notches and surface treatments out. Every time I have a piece to make on the wire EDM I add in a rear sight blank if there's enough material.
