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.
