Posting this, since a fair few people seem to have asked about it on the internet but no-one really had an answer.

If you are looking to add a optical media drive ( CDRom / DVDRom etc), just keep in mind that its a conventional atapi slimline drive that fits into the slot in the front. Its literally a case of flipping down the front cover, and sliding in a drive. I 'borrowed' a dvd drive from an old laptop, removed the mounting around the drive and pop'd it into the running machine. OpenFirmware was able to detect it right away and quite happily went through a 'boot cdrom:' process.

- KB