After much trial and error, I finally got a 9.2.2 install up and running on my 800 MHz 17" iLamp (using the NetBoot OS 9 download image as the base.) That install does not boot my first-generation 12" Aluminum PowerBook G4. As far as I know, that iLamp is the last Mac to boot OS 9 (not counting "prior generation Power Mac re-released solely to keep an OS 9 bootable system on the books",) and uses the same graphics chip as the 867 MHz 12" PowerBook.

It has always been my understanding that the Aluminum PowerBooks simply cannot be made to boot into OS 9.