I have a RS but don't know much about Linhof sliding back. From my experience with KaptureGroup sliding back ("back then"
) - not for the RS but for the LF system- they have various digital plates for different digital backs to align the distance. "IF" Linhof sliding back mounts onto the WRS, the sliding back viewing glass will allow you to focus to that plane (which would be the same to the digital back on the sliding back) and that should work. If the distance is off, it should not matter because you are focusing onto your new reference plane and is therefore based on what you are seeing. I know there are a lot more experts on the forum than myself that will assist. My reply is merely my hands-on feedback.
NB: Back when RS first came out, I had asked KaptureGroup if he could come up with his own sliding back design for the RS. I too asked Cambo if they would make one eventually.
Good luck...