I stumbled over this article http://www.lowendmac.com/practical/02/0507.html Maybe this is of help for some of us. Anecdotal notes: I remember for anything other than simple word procession OS 9.2.2 in Classic mode under Tiger on an ibook 2005 with 1,33GHz had stuttering mouse cursor movement. So maybe this does help. I didn't try it myself though, since I have Macs that can natively boot into OS 9 that I use instead, if I need OS 9. (Interestingly 9.1 under 10.2.8 runs fluently in Classic mode on an iMac G3 DV, its interesting that it runs weaker on the faster ibook).
There was a period of about six months or so where I was running 10.2.8 with Classic on one of the G4's at work. This was so I could run QuarkXPress 4.11 and Suitcase 10. I simply disabled all the extensions I knew I wasn't going to be using. Worked fairly well. Suitcase 10 is a transitional font manager. It runs under OS X where you activate fonts, but due to the OS9 extensions it installs it makes those fonts available to OS 9 apps such as QXP 4.11. Other than the tendency to have to force redraw the screen on occasion QXP 4.11 was pretty stable. There was an XTension (Quark XPress plugin) created at the time for that.