Rather than "play" with life size blocks, I would cut them out of 1/8" or 1/4" graph paper, with one square per inch, using a solid piece of graph paper to lay them out. Do the sizes of your current list reflect the actual size that you interfaced and cut, or just the size of the center motif? If possible you may have to trim some of them down to fit or add not only sashing but more or less shirts. Just play with it like you are arranging furniture in a room.