Sweet, figured out the problem, the Atmega8 has a different clock multiplier than the 48/88/168/328, so the fuse bytes were wrong. Setting the correct clock multiplier fixed it right up
eggwolio, if you're wanting to buy populated and programmed boards and do the mod yourself, take a look at the photos. You will need to remove the white pin header from the controller's PCB (not shown in the photos, I'd already removed it), then simply align the holes on the adapter PCB with the ones left by the pin header, stick pins through the holes and solder. I used 22 gauge wire that I just snipped to the right length, since the pins are a non-standard pitch, so you can't get "real" pin headers for them (not easily anyway, and it's only 5 holes, just run the wire through, solder to one side, snip it to length and solder the other side. Just don't heat it too long or the wire might come loose and stick to the iron. Then, just attach the wiimote cable. The silkscreen labels match up to the OEM cable colors, but no guarantees if you use 3rd party cables. You don't need to attach the bare shielding wire if there is one, I just clipped it short. Here's the signal/color pairs:
Y - SCL
G - SDA
R - Vcc
W - Gnd
The pads on the bottom of the PCB are for programming the microcontroller, and can be left alone, since it will come pre-programmed.