Your tape solution will work just fine.

FYI, you can also make up new DX labels using aluminum metal duct tape that you can buy at hardware stores. You then tape over the duct tape with bits of electrical tape to make up the DX code. This is useful for bulk cassettes or completely changing the ISO rating. For instance, sometimes I like to underrate films by 1/3 stop so I hack the DX code to make up what I need. Works great.

Wikipedia has a page detailing the DX code.