I added this to the main thread but was not sure if it needed to be here as well.
One additional add if possible (someone mentioned it already) would be a "View" or some button that when pushed shows you the layers (selectable would be awesome) overlaid so you can see how the layers line up together. I did the copy/paste from a previous split file project and the only way now for me to verify that the alignment is correct is to carve the entire project out (not ideal). If I could click both layers and see them on the overview I could confirm/tweak as needed. If its something you can add later it would be awesome!!