Just finished a backup light mod similar to the ones posted. I used 12VDC GROTE rubber housing floods. I put 2 on the rear where the stabilizing mounts are and 2 in the front facing rear and outside the tires on the stabilizer mounts on the frame. Never had to drill a hole. I used a relay with supply 12VDC coming from the trailer battery and the switching coming from the yellow pigtail wire. I added one additional step. I ran a wire to the powered tounge jack's light switch with a diode in line so when I was backing up, the jack light won't turn on and distract me. I conntected that wire with the yellow wire providing the switch for the relay. Now I can turn on the lights without the truck hooked up. Should be great for the night time dumps and additional night lighting around the TT. Hope to take some pics tonight and I will post.
2013 Cardinal 3800FL
2009 GMC 3500HD CC LB SRW