You know… I don’t know if this will work, but you MIGHT be able to use your G4 as a “capture station” only. You would just do all your digitizing from here.
Then, you put the software only version on your G5, and use it to edit. You might have to manually switch your scsi drives (or figure out your specific storage issues), but then you could still get the best of both worlds…
Lossless on the G5… no expansion chasis.
…just a thought.