Ok, so i have a flat 4 trailer harness on my truck, and am installing a flat 5. I will leave the current flat 4, and splice int eh flat 5 too. What are the best wire taps to use that are reliable and fairly weatherproof? Also, the 5th wire is the backup light wire. Where is the best place to splice into that circuit? Its not part of the trailer wireing harness behind the hitch. Thanks guys! I'm excited to finally have a plug that will work wiht all teh surge brake trailers i tow so i can take advantage of the backup solenoid.