Has anyone successfully used a real power pad with snac?

[yatzr]

I picked up a power pad today and can't get it working correctly with mister fpga. As I'm searching around, I can't find any evidence that anyone has made this work. Unfortunately, I don't have a power pad game to test on a real nes.

In the core settings, I'm using "Swap Joysticks: Yes" and "Serial Mode: SNAC". All other inputs are default. I've tried the NWCS Power Pad Test Cartridge (just says a powerpad isn't connected), Dance Aerobics, World Class Track Meet, and Super Team Games. On the 3 latter games, only pads 2 and 4 register anything. In Dance Aerobics, it shows me that when I press pad 2, it thinks pads 1,2,5,6,7,9,10,11 are all pressed at once. And when I press pad 4, it thinks 3,4,8,12 are all pressed.
I disconnected the pcb from the power pad and manually made "button presses" by shorting the pads and got the same result. I also checked continuity of the pad itself when stepping on the buttons, and they're all fine. I thought maybe the 4021 shift registers could be bad, so I tried swapping them with shift registers from nes controllers, but I still got identical behavior. At this point, I'm wondering if it's actually the core.

[yatzr]

I picked up a dance aerobics cart for cheap and was able to confirm that my power pad works just fine. So I think it's just the core doesn't properly support the power pad
I suppose it could also be something with my snac adapter, but I haven't had an issue with any other peripheral I've tried.