The 8GB limitation was only for Beige G3s and Tray load iMacs. AFAIK the B&W G3 can have a partition of any size for a startup volume, and in any location on the drive. (the Beige G3s and tray load iMacs also required that the 8GB or smaller partition be at the beginning of the drive)

I'd say the problem might be with the Twin Turbo card, if I'm correct that card was never supported under OS X...try swapping it out for a supported ATI or Nvidia card if you have one handy.