Bicycle Brake Cable Splitter

I'm in the process of building a lean steering, recumbent trike and and need to split the control from my front brake lever to both the front, mechanical disk brakes. I've only got two hands, but a recumbent trike has three wheels and three brakes. I need one hand fro both front brakes and one hand for the rear. Yeah, I could buy a dual pull brake lever, but I have 2 perfectly good levers in my junk box and the point of building a trike is that I don't have a lot of money, otherwise, I'd just buy a Trisled from down the train track, in Morwell.

So, how does a brake splitter work?

If you look at the first picture, you can see the cable sheath from the brake lever entering the single hole on the left, and 2 brake cable sheaths leaving on the right, one for the left-hand front brake, one for the right-hand one. This bit's pretty straightforward.

The cutaway view (second pic) shows the internal slide. Threaded through the side holes in the slide slide are 2 road bike cable inners.