I’ve been pretty much following the order of build page-by-page in the manual. Once I had my door sills in, I moved on to the shelf. It took a lot of pounding, tugging and persuading to get the shelf in. Fortunately, it finally slipped into place. If I had needed to take it out to trim anything, I don’t think that it would have been possible. The door sills were in the way. The manual shows the shelf being installed without the door sills, but for some reason, these pages follow the discussion of the door sills.
Another tip: open any mortises before covering them with anything: door stiffeners, door sills, the aft end of the galley hatch. This is obvious in retrospect, but, again, I was following page-by-page. I used a Dremel to clean out the covered mortises, but it would have been a lot easier to be able to poke a file all the way through.