Here is a bank that I saw Efren hit in a game against Thorsten Hohman. Efren saw it, and hit it in the middle of a game. I recreated it on my table. It took me 5 attempts to get it. It really teachs you the mechanics behind a double bank. When it hits the second rail the deflection is dead. Look at the small angle off of the second rail in my video. I do not know if efren and hohman's video is still on youtube or not. I was able to hit it but would never have the balls to do it with cash on the line.
http://www.youtube.com/watch?v=BG4junjpKu8
http://www.youtube.com/watch?v=BG4junjpKu8