4.3G should be fine. Its the old 32-bit unsigned integer limit value.
The patches you are referring to were official, IIRC and are built into OS3.5 / 3.9 as standard. I'm using a 10G drive on my OS3.5 A1200, no problems at all, bar one - ReOrg wont touch the partitions not inside the lower 4G limit :-(
Alternatives for large drives are third party filesystems such as SFS (which seems to be a favourite).
