If you are having bother positioning the support posts to hold your Fez Mini robot together you might find the above picture useful. The PDF gives lots of good detail about how to fit the motors to the battery tray, but lining up the unit with the right screw holes on the base is a bit tricky. I think mine is right, at least the wheels seem straight enough for me. The back of the robot is at the bottom of the above picture.
Oh, and you don’t have to fit the line detectors where I have (just outside each wheel). This is part of an experiment I’m doing to find out how well grey scale line following can be made to work.