If you are going to tow with a 16ft trailer, you might want to go this way:

Use a 7 pin connector utilized this way:
1-Ground
2 and 3- Left and Right turn/brake lights
4 Parking/marker lights
5 Power to brakes from the controller
6 Back up lights-optional, but very, very useful
7 fused, constant power to the trailer for the winch (switched).

The actual wiring schematic of the plug is as found on various sites, but the utilisation of the pins is as above.

First order of business, though, is to establish a solid ground (fresh, clean contacts) from tow vehicle (TV) to female receptical, and another solid ground from the Trailer Chassis (TC) to the male plug. All other efforts may be for nothing if the ground does not exist as specified. Recheck the ground for each accessory (lights or brakes), clean the sockets or replace the lights as needed.

My advice is to solder all connections, and smear with a sealer, and then tape or shrink wrap for weather protection. Crimp connectors are for emergencies, and are very bad in the North East.

Put the required time into it and it will pay dividends for years of reliable service.

Good racing.

Bill