For a personal data point, I have just confirmed this works well in my PM 7600 running OS 8.6 and OS 9.1, and mostly (apparently without acceleration) in OS 8.1. Note that this is the actual retail Mac Edition PCI 9200 with 128 MB of VRAM which is overkill for this model, but I digress. I do it because I can!
I downloaded the file '9200os9.sit' from here:
http://www.kranenburg.cc/mirko.cc/macclassic.html(I've seen links to the Howfunkel site, but when I use Stuffit on that archive the file types are gone and not recognized as extensions. At this site, the file unstuffs fine.)
Then I made backups of my 8.1, 8.6 and 9.1 extensions folders. (This is a tricked out 7600 with 512 MB of RAM, a Sonnet G3/300 card, and a Sonnet Tempo HD with a 120 GB "SSD" -- really an mSATA card and mSATA to 2.5" IDE adapter -- attached to the card with partitions for several OS installs, shared data/apps and other stuff.)
With my previous video card -- a Rage 128 with 16MB of VRAM -- still in place I began to move the files -- it's best to install these while the old card is still there. I rebooted with extensions off and copied the 12 files in the new "9200os9" folder into my three Extensions folders once I had a good backup copy of each. I rebooted once into 9.1 with the Rage 128 to confirm it still worked fine. It did.
Then I shut down, replaced the Rage 128 with the 9200, booted into 9.1, and it all worked fine. Next, I booted into 8.6. Again, worked perfectly.
Finally, back to OS 8.1. It crashed on an extension while booting up. Trial and error indicated it was the "ATI Resource Manager" extension which was the culprit; removing it and leaving the other 11 in place works *except* that the acceleration extension is "X-ed out" when loading at boot time. Other than that it seems to be working fine.