Hi,
did you try other filesystems like PFS3? (Aminet)
PFS3 can use "DirectSCSI"-commands in NO SPLIT-mode for handling partitions/hdd >4GB (PDS\0 as DosType).
FastATA'99 offers you the following support for HDD > 4GB:
1. SPLIT: dividing a HDD into logical units > 4 GB,
2. NO SPLIT: FastATA'99 supports the following:
NSD (New Style Device - OS3.5),
TD64 (TrackDisk 64)
DirectSCSI commands.