Setting custom widths for all the columns in the edit section appears to have no effect on the table when it loads. All the columns get resized to ‘width:25%’ no matter what values I set them to in the edit section.
The only way to ‘fix’ this has been to remove the file called ‘frontend.tables.js’, which has the adverse effect of stopping me from editing the table afterwards (i.e. the file needs to be present if I ever want to be able to edit the table).