If I am understanding what you are describing, 80/20 already makes them, and Im sure Bosch does too.
[Edit]
http://www.8020.net/pdf/Fractional/07%20Section%204%20(03-186).pdf Item number 4042 on page 112. Those things do get rather expensive as you start to use a lot of them, so I can see why you would want to make your own. We are thinking of spending a few days dedicated to nothing but fabricating connectors for 80/20 to cut down on costs.
Cory