I realise I should have waited until the end before making the dust jacket. Now it doesn't fit - I've seen it in a printed draft. I cannot delete the cover and start it again, it seems,, only alter the padding around the images or replace them, which may be enough. But are the guidelines in the right place now the book is thicker?
You should be able to modify the dust jacket at any time, without deleting.
Can you describe in detail what you mean by- "now it doesn't fit". A screen-clip?
I compared two of my books (160 vs 20 pages) and the width of the spine did alter with page numbers, so I assume that guidelines do change with book thickness.
Thank you WobertC for confirming the guidelines do change. I altered the position of images on the cover yesterday and it seemed ok so I don't have an image direct from Lightroom, but I wasn't able to say if the guides had updated themselves while the book was getting thicker. The images here are of what it's like now and from the printed version at an earlier stage with no lettering on the spine. As the book is a 12x12 square, 240 pages it's an expensive purchase to get wrong. I feel a lot more confident now. Thank you for taking the time to answer my query.