placing sub assemblies

I'm having difficulty placing these parts & sub assemblies in the photo below. The pivoting brackets are sub assemblies with a pin constraint. I'd like the top bracket to move along the vertical 80-20 post if I change the length of the 80-20 kicker, so I have been using a slider constraint. I get to the point where I am trying to connect the 80-20 kicker to the bottom bracket, but I'm getting invalid constraints. Any help is much appreciated!