TOPMAX Dreamcast controller

Does anyone know if it is possible to dual mod one of these with a PS2 controller to put into one stick? I could take pictures of the pcb later if you need. Does anyone know if its common ground? The directions are wired strangely on the switches - they don’t seem to have separate ground wires, but they share some wires (its different than i’ve seen before)

Here is a drawing of the directional wiring

ooh, that was my first pcb hack ever back in '01/'02. i doubt it’s been revised, so yeah it should be common ground. i had the purple one tho and it would enable turbo sometimes when i plugged it in. never wired a turbo button so i would have to replug the stick every time it happened.