Disk errors on PowerBook 180

Hello,

I'm attempting to install NetBSD 10.1 on my PowerBook 180. I have an extern=
al BlueSCSI connected to serve as the disk for NetBSD.
Only the SBC kernels will work with SCSI on this machine.
sysinst cannot format any partitions. The command

/sbin/newfs -V2 -0 1 /dev/rsd2a

fails with

newfs: /dev/rsd2a: open for read: Device not configured

And now the partition table is broken.
So I start over, formatted the NetBSD root&usr partition in Mac OS using th=
e Mkfs program and installed base, etc, kern-GENERICSBC sets using Installe=
r. Booted into the new system single-user, I run fsck. It says

FREE BLK COUNT(S) WRONG IN SUPERBLK
SALVAGE? [yn]

If I choose yes it then breaks my partition. Mind you the disk is 512 MB so=
 the NetBSD partition is below that size. I previously used a 1 GB disk whi=
ch had the same errors.