Just installed a Laser Interceptor and hardwired V1 and wanted to add to this thread. The ground is next to the driver's side fuse box, slightly towards the front of the car. Here's a picture. The silver nut is out of focus, but can be seen just right of the zip-tied wire bundle and left of the shop light. Hope this helps.

 

Thanks again guys, just diving into this with my 2015.

 

I just finished Bel STIR PLUS install by adding "add a circuit" to ncamg's driver fuse panel location. It turns off and on with the ignition key.

Thanks, ncamg!