Creating a tower with several drives is the best solution for multiple external drives because it reduces the length of the SCSI bus. However, I wouldn't want to have six or seven drives in a single unit. It is a bit inflexible if you want to share the drive unit between multiple Macs. You may also want to connect an additional SCSI device to the chain at some time (a scanner, tape backup etc) so full occupancy will create pain, unless you have another SCSI adapter.

Do you have a SCSI adapter for this unit or are you planning on running it off the external SCSI II port on a Mac? For performance reasons, the latter is not recommended.