I laid out 14 of the 28 chapters today, as well as making the changes (like resetting the margins) that had to happen in all the chapters. It went well--I'm halfway through and the book is 16 pages shorter than it was, which bodes well for getting the large-print edition in under 820 pages.
I've noticed that if a change needs to happen in every chapter, it's easier and more reliable if I open them all up and make all the changes at once. In the past I've tried making a list for myself and then checking it off before I lay each chapter out, but if you skip something (and I have), then all your laying out is for naught and you have to do it again.