Hey, Moira, a little off topic but wanted to mention I'm making a top based on the picture you shared a couple of weeks ago made with bright 5" charms and white. I was gifted a box of pre-cut squares in various sizes and themes with a lot of bright bold juvenile prints and used your project as inspiration. I'm keeping with 30 focus squares but mine are 6.5" raw edge. Since the sashing doesn't need to line up I'm also using 6" blocks to cut down the sashing, they will all be consistently 3" raw wide even if the length varies a bit.
So my top will be quite a bit larger and may be an awkward size and may require an extra row or something. Haven't fully visualized the finished top, this is one of my slice and dice projects and I'm trying to break free from my usually tightly controlled self to just roll with the punches, or the gift fabric as the case may be. However it turns out, I'll let you know.