Am I right in thinking I'm limited to 4 gigs? I'm running Workbench 3.1 on 3.0 ROMs.
Yes, but this is a software limit only. You can buy a drive up to 128 gig. As long as you create partitions only in the first 4GB of the drive, you are fine. Software to use the rest of the drive can be installed later.
However, with Kick 3.0 you should be prepared that the HDD is not found after power-on (either sometimes or always, depending on the drive and the weather). You might have to press Ctrl-A-A once in order to boot from HDD.
Bye,
Thomas