To get to BoingBag 4, you need KS 3.1 ROMs and an install of OS 3.9 + BB 1 & 2; I don't know if you need BB3 to add BB4 or not.
OS 3.9's FFS is 45.16 which does large drives. PFS & SFS are faster, but not really recoverable, so make frequent backups of important partitions to some of the extra partitions on your 18G HDD. FFS is pretty resilient and recoverable, plus reasonably fast with enough buffers.
Mech is the A3000 OS install guru, so drop him a line if you want definitive help.
I finally got WB31 installed. It refused to work as an upgrade to WB21 so I had to wipe it and start fresh. There is a problem with installing PFS3. I found it on Aminet and downloaded it, extracted to a work directory in the hard drive, but it fails to install. I tried copying to the root of the ramdisk but it still will not install.
I think it has to be on a CD but I do not know how to extract to my XP box and burn a disk without destroying the long filenames for Amiga.