This time I used a different approach. I did a `clean' 9.1 installation, followed by `patching' my 9.1 installation to do what my 8.2 installation could do.
In fact, the 9.1 installer does offer to upgrade a previous 8.2 installation and actually did so successfully. There were various RPM conflict issues, of course, but it seemed to do a good job. However, I opted for a clean installation because...