dug 
I forget if I mentioned this already, but those of you using an iBook by accident (as in you really need to be on a Powerbook but tricks of fate etc etc) might want to modify the Open firmware to kill mirroring. Instructions to re-enable the “arrange” tab in the monitors control panel are here
If you have no idea what I’m on about then no need to worry really;-)
Btw, I tried this on a recent (32meg vram/800) iBook, but it appears to work well on several generations.