Having shot with both the 1DX and RZ67 II w/MFDB, I would say that you've set yourself a lofty goal.
With the RZ67 shot wide open, I found it was easy to see focus misses of just inches, even at a subject distance of 10 feet. The glass is wonderfully sharp with a great rendition, but I found it took a high degree of precision for focusing. I ended up using a 6x loupe directly on the focus screen through the waist level finder, but obviously this won't work for your purposes.
I'd look at getting the best possible focusing screen (maybe a brightscreen or a maxwell?), perhaps adding a flip up finder magnifier to your prism, and practicing a lot. That, and learning to be okay with a lot more focus misses.