Installing a 7 blade receptacle on 2012 VNL 780

I've been working the past few days setting up my truck to haul RVs and other trailers with the 7 blade connector. My first thought was to just take an old pigtail and put the correct function to the receptacle. It would be a bit easier to just have a separate pigtail. This mostly worked, except for the brake lights on the trailer, and I still needed to run a different wire to the electric brake controller.

So I bought a converter to combine the stop lights and turn signals on the trailer. Finding the brake signal was kind of tricky. There is a switch at the pedal, but it works the opposite of what I'm wanting. It has 12v running through it normally, and it cuts the voltage off when you apply the brake pedal. I'm guessing this is how the cruise control gets disabled when brakes are applied. I also found out that the brake switch, wherever it is located, is activated by air. If we press the brakes while the system is empty, it does not apply the brake lights. We ended up running a wire combined with the 87 pin on the relay for the trailer stop lamps, and it works. Is there a better way to do this than having a wire sticking out of the front of the relay and fuse box?

I will get some pictures of our setup for anyone who is interested as well.

 

Sheathed the wires up and zip tied it up along the frame. I'm still working on cleaning up from the batteries to the engine bay. The conduit is only rated to 176F, so I don't think I'll put it in the engine bay.

 

The only benefit I could see to that system would be if it were plug and play, but it looks like it comes with spade connectors to splice into the wiring for a signal. It would be $256 to get their converter and wiring harness, and it doesn't come with a brake controller. I spent like $50 on the converter box, $60 on the brake controller, and probably less than $100 on the receptacle and wiring.