No, the whole rear ring will be different. I get the feeling though that a lot of the bigger cams don't have a perfectly lens centered image..in which case the XY adjustment will be very nice to have. If the cam image is lens-centered, then adjusting XY will only result in the cam not being aligned to the max size image cone from the 35mm lens...which is not a good thing.
Given the current GG size, an adapter should be able to tolerate about 1 to 2mm of gg/cam XY misalignment, and still mainain 24x36 frame size. It's likely that the next run of diffussers will be 1-2 mm larger in the x axis to give a bit more leeway. That way the GG plate XY orientation is not that important. Z axis accuracy is far more critical to maintain sharp focus across the image plane. Z axis alignment and incorrectly sized achromats are likely to blame for 95% of edge to edge softness issues.