I believe the double trim switches are part of most autopilot systems.  I had them on my Mooneys with King autopilots.  The are more than just in series.  They run back to the autopilot to detect a stuck trim switch.  If only one switch is closed for several seconds the autopilot detects a stuck switch and disconnects.  I'm sure you could wire the switch(es) in series however.

 

Mike Easley

Colorado Springs