I was going to do this a while back and even opened a thread on it, because i thought i had a "deal" on ebay for 5 drives. Turned out the seller was a deadbeat and at least he finally refunded me. So after that happened, I abandoned the project.
I was going to use a DC-DC circuit stuffed inside the powerbook somewhere. I was actually going to physically remove the backplane connector and adapt over the PB SCSI cable. Also somehow fit a terminator in there, as one is required in this sense.
Main PC: Intel core I7 920, MSI x58 platinum, Radeon4850
PB: tibook G4, ibook G4, Lombard, 160, 165, 180, Duo 2300x2, Duo 270c x2, 520cPPC, 3400c, 1400c
Desktop: G3AIO, 5260/100 x2, SE, SE/30, 512k, plus, LCIII, 7100, iMac G5 iSight, 6400/225