It may make more sense to put both the Sketch and Textless pages in the same posts, which means less clutter and eliminating the Sketch and Textless tags, and simply using the bts (behind the scenes) tag.
Only difference is, you can't click on the pages here to view the full version. But they're still plenty viewable, and you do still get the original PNG files at the end of each chapter.
Would you be okay with the BTS pages being bundled together? Did/do you have any use for the Sketch and Textless tags being separate? Let me know!