When I was removing the second row seats from my 2015 LWB wagon, I noticed some of the factory wiring harness running forward under the front row seating on both sides. I can't give you details because I didn't go any further with my dis-assembly in that area. But you may be able to use the same channels the factory wiring uses to run your wires in. Here's some pages from the 2015 wiring manual that show the factory harness routing from front to back.