It took them a month but finally X-Gaming confirmed that their controllers
do not work with Mac OS X Leopard without the extra Mac/PC Adaptor they sell separately...
But they still advertise and sell their controllers without the adaptor as "fully Mac compatible"...

Anyway, i replaced the low-quality Tankstick joysticks with the excellent programmable U360s from Ultimarc. Each joystick controls up to 8 buttons (one button works as a shift key, so you can program 15 different keystrokes).
The U360s work fine with my Mac and can be programmed as 2-way, 4-way, 8-way, 4-way diagonal, full analog, or anything else you like!