Ah, that's a digital joystick. Star Wars uses an analog stick. So you need to do exactly the opposite of what I suggested: map the individual up, down, left, and right inputs, but leave the AnalogJoyX and AnaloyJoyY unmapped.
This will end up simulating an analog stick by incrementing the axis value over time when you press in a given direction. Not sure how good it will feel. The increment and decrement rates are configurable by editing Supermodel.ini directly but you'll need to read README.txt to find the name of the settings (because when they are set to their default values, they do not appear in the config file).