Avionics: Oil pressure switch

My panel design includes a Hobbs switch and an "Oil" indicator light.  I wanted those to function as as result of operating oil pressure.  Thus, I needed to add an oil pressure switch to the VA-168 Sender Mount on the firewall.  However, the circumference of that switch requires the Sender Mount to have a spacer underneath it.  This trail was blazed by previous builders.  I merely copied them.

Here is the 1/8" spacer after cutting and match drilling it.

Spacer installed.

Oil pressure switch apparent.  I obtained it from Van's, part "IE SPDT PRES-15 SW".  It's manufactured by Nason, part SM-2C-015F.  I later redid the common wire as the one in the photo broke after mild handling.  The wires passing through the firewall have not yet been secured with fire sleeve and RTV.

This switch has three terminals:  Common (C), normally open (NO) and normally closed (NC).  The C goes to ground, as shown by the black wire above.  The yellow wire goes to the "Oil" light on my panel and is connected to the NC terminal.  This provides ground to the panel LED when the oil pressure is <15 psi, thus switching the LED on.  When the oil pressure exceeded 15 psi, the ground is removed and the LED turns off.   The NO terminal is connected to the HOBBS meter.  Thus, when the engine has oil pressure >15 psi, it provides ground to the HOBBS (which has +12V when the master is on), thus turning it on.

Here's a shot of my panel's independent indicator lights.  Here, you can see how I made the test circuit so when you press the switch on the right, all indicators annunciate (to determine if any lights are burned out).