To the best of my knowledge :
1. For FWB to resize partitions on a device it has to be using FWB drivers.
2. Exercise caution : if you install FWB drivers on an unsupported device anything, meaning ANYTHING, can happen. I recently installed a Seagate drive [ unsupported ] as a slave in a G4 with a Western Digital drive [ also unsupported ] as master. Seagate was toasted - twice - I am on my third replacement drive from Seagate. Both now have Apple drivers and all is well.
3. FWB also has trouble even mounting volumes with Apple drivers installed. I am using 9.04....
Hope this helps.
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OS 9.0 Mac OS ROM 3.2.1
G4 350 128 MB RAM
SCSI CARD ADPT 1686806-04