Once you modify "qWidth" you will need to close Qlik Sense, reopen it, and convert the old rendering of the table into the new rendering by dragging and dropping and selecting convert (if you are planning on altering an existing table with the updated extension code). The initial properties of an extension are rendered at the time you first create the object on the page. For any changes in the JS's initial properties to be reflected, the object needs to be recreated.

Screenshot: http://imgur.com/CdxHA99

Cheers,