While working on the Ignition Jitter problem I took the opportunity to measure the distributor cap and rotor electrodes and to check if a more optimal orientation was possible.  When putting this together Edelbrock gives you a small indexing jig to orientate the cap to the shutter wheel.  You have to take it on good faith that they did their homework because it is not easy to see exactly the orientation of the cap to rotor and the relationship to when the coil actually fires.  When I installed the Crank Trigger I needed to set the placement of the distributor independently of the timing light.  You can twist my distributor all day long and it don't change the timing any more !  One of the things that I noticed was that there were the signs of arc tracks leading to the electrodes in the cap.  This system is highly advanced and it looked like the rotor was too far ahead of the cap's electrode most of the time.  So before I lost the actual timing of the engine I found a old distributor cap and hacked a section out of it so I could more easily see the relationship between the cap and rotor electrodes.  Below is some measurements of cap and rotor electrodes I had laying around and what was on the car (MSD cap and rotor).
 

Below shows the relationship of the Cap electrode's to the Rotor's at various timing advances.  This is how Edelbrock's jig positioned the rotor to the firing edge.  As the ignition event occurs, which can be in the range of 1ms - 2ms, the rotor is of coarse still advancing.  You can get too aggressive at centering these electrodes or at higher RPMs the gap might start increasing instead of keeping the maximum overlap.  When I re-installed the cap I only moved it about 5 degrees more advanced.  Still pretty safe as most of the time the spark advance is in the 30 to 45 degree range.