after you run the script, you'll need to close and reopen the font for the change to take effect. (I've just tested it again in RF3, works fine) another solution would be not working directly on a server or DropBox folder, if possible. you could ‘check out’ the font to another place, edit, and then check it back into the server. (or use a version control system like Git, which works just like that; see this tutorial in the new docs.)