I have some interesting things to report. As I mentioned, I have a firewire drive, which is connected to my mini. This drive is from an old computer I owned a long time ago that ran on OS 9, and the system files are still on it.
On a whim, I decided to copy the modified Mac OS Rom file from the newly-created Installation CD from this site, to the System Folder on my non-booting OS 9 stuff on the firewire drive. Now, after re-starting the mini and holding down the option key, the firewire drive showed up as a boot option.
When the boot process was complete, I got the same garbled text and images I was getting when I booted from the Install CD. As I clumsily navigated through the garbled mess, I was eventually able to find the Monitor control panel and change the resolution. The highest resolutions that worked were the 1280x1024 (60Hz), and the 1024x768 (both 60 and 75 Hz). All of these created stretched images of course, because my Dell monitor has a native resolution of 1920x1200. But the images were clear (without garbled text or graphics).
I must confess, I was hoping to be able to play an old Ambrosia Software game called Barrack (which doesn't work right in the Classic environment) but unfortunately, the balls in the game don't move correctly even in the OS 9 environment. Drat!
Maybe, installing OS 9 from this specially-created Install CD onto the internal mini drive will yield better results, but I have my doubts. It would be nice if the resolution problem could be resolved somehow. Just to be clear, the monitor displays perfectly in OS 10.4 as well as in the Classic OS 9 emulation environment.