USB booting :: Update to version 1.0rc1

I have a USB key with dsl-0.9.2 on it. I want to take it up to version 1.0rc1, how can I do this. Can I just update the KNOPPPIX file or do I need to install from scratch. Can I leave my optional directory in tact ?

Thanks in advance
Simon

Only the KNOPPIX file is required.

original here.