My engine electrical system may look somewhat complex.  I'm using a dual ignition system as per the instructions of Paul Messinger.  See my engine pages for details. 

In accordance with proposed electrical architectures in the AeroElectric Connections, I use a contactor to totally disconnect the alternator when turned off.  Apparently, some failure modes may allow the B-Lead to turn wild.   I don't have a large breaker in the cabin for the alternator.  I'm using a current limiter (big fuse) in front of the firewall.  I also use a separate starter contactor.  Bob (AeroElectrics) has a good explanation for this on his web site.  On top of his justifications, I felt it allowed me to completely build my electrical system (except for one connector to the starter) even though my reduction drive and starter are not in place.

The EIS system generates quite a few wires in this area since all senders are electrical.

You may notice a small relay in the center section of the firewall. This is my automatic tach selector.  I'll see if it works later.  When ignition 2 is off, it takes the tach signal from the ignition 1.  And it takes it from ign 2 if ign 2 is turned on.