As I expected, the DCP profile created by the Calibration software from my own ColorChecker shot is giving me a DE00 of 18.85 which is not very good IMHO. Using my workflow I can get that down to < DE00 2, which should be enough for any reproduction work, or a pretty good starting point for any colour grading, and it would give the same results whatever the camera that was used. For general photography, your workflow, may be sufficient for most people however. A quick note, a DE00 of 1 is considered as a just noticeable difference.