Achievement Unlocked: RTFM

“Any controller that uses the Atari digital joystick standard will work with these products. Included are the Atari 130/400/800/2600, Commodore 64, Sega Master System, and others. Analog controllers like the paddles are not supported.”

http://www.retrousb.com/product_info.php?cPath=25&products_id=46

Well…  So much for that idea.  Unless I can get a Stelladaptor in the next hour somehow, I think that plan is out.