How are you guys running your wiring harnesses for a trailer? I've read a few posts about using a basic flat 4 harness for LED trailer lights, but I sometimes rent old Uhaul trailers, which have the old school incandescent lights so need something powered. Therefore I would like to install the recommended Tekonsha 119250 (no splice) harness on my 2013 P85, but not sure how to wire up. From what I can tell person with ICE cars route this to their 12v battery, but it's such a pain to run cable up there so wondering if there is an easier or better way? Will the license plate lights or power lift gate be enough to power this harness? Also anyone install one of these and have the wiring diagram? Some previous posts pair up the L, R, lights and ground to a singe (L or R side) of the tail lights vs. another member said you have to run from BOTH L and R taillights to each of the harness wires? Any thoughts or help with this wiring would be appreciated.