I've decided that this: {author_sort[0]}/{author_sort}/{series}/{series_index:0>3s} - {title} - {authors} is a good way to view books on my device. Previously I had: {author_sort}/{series}/{series_index} - {title} - {authors}.
The question is, how can I get Calibre to restructure my folders without selecting my whole library, deleting & resending to my Pocketbook 360?