Do any of you know if the "add-on" cards do something specific with the signal?

I'm thinking about drilling 4 holes in an ordinary back plate and put RCA sockets there. Then connect the RCA with cables directly onto the SPDIF pins.

Edit: I simply want this to feed the g68 with 3xSPDIF containg the decoded PCM/Dolby True HD from HD-DVD and Blu-ray.
Edit2: Ahh .. now I see the image from Tommy, pretty much answers my question that you can connect directly onto the pins.