P: Book module dust cover

I've tried the dust cover in my latest draft, and the only way I manage to edit it to include left (at beginning) and right (at end) inside covers is by trial and error with front and back covers.   That is, there should be FOUR parts to edit - cover, back, AND left and right inside dust cover.   Plus I can't move anything around on the dust cover.   I have to go back to develop and change/crop size.  Am I not seeing something?   Or should that code be updated to work for the 4 images of the dust cover?