The simple representation of the mounting arrangement provided by the manufacturer leads me to believe that they've been inspired by the old Jandd attachment system. Otherwise, I'm not familiar with Two Wheel Gear. Take a look at the mid page section of the link I provided and see if yours works like the Jandds.
http://www.jandd.com/Technotes/technotes_panniers_1.asp
What is the measurement from the top of your rack to the lower pannier attachment point? What brand and model of rack?