With the new unibios 3.1 with added card support, this project should continue. I finally got the time and located the pins on the GRZ that could be CD1 and CD2. There's 4 suspecting pins, I have to try it carefully or I could burn a MV1C.
David has already tried all the pins on the GRZ. You will kill the GRZ.
1C systems seem to have the biggest problem and required a modified bios. The 1B could be done without modification, supposedly.