Nice once again.
Funny, it brings up an issue I have with white tile-board.
Even overlapping them correctly, I still get "seams" that have to be dealt with. Easy in most cases, but when you to a shadow under the subject or some such, the removal isn't as easy as I would like.
Have you thought about some sort of white tape or some such to join the boards? I'm afraid I'd end up with a seam with that too, but I may try some. The boards would still be "hinged" that way so they could fold up, but maybe my processing would be a bit easier.
That or find someone who can get me an 8x8 tile board!