I remember killing a whole week trying to get Mac OS 8.6 to run on a Quicksilver for a specific client.. swapping MB boards, trying different ROMs, etc. In the end, nothing worked... the "The Rule" as you mention it, Chris, was a hard lesson to learn.
Apple always had a nasty habit of moving forward with ROM versions, It would have been nice to have had a "legacy" G4 ROM version for newer hardware, that would work with at least OS 8, but guess that would have been too much work.
Thank God, guys like iMic, said "No thank you" and didn't give up when Apple said... "It's our way or the hiway"