I've spoken with the pattern writer, who mentioned 1/4" vs scant 1/4" seam allowances. I used the same scant seam allowance I always do, meaning the outcome after sewing a seam results it losing 1/4" in the size of the finished piecing. She had changed her seam allowance from 1/4" to scant 1/4" at the end, which I have never come across, so the end result was her finished Star diamonds came out smaller than mine (and I would guess not a true 1/4" seam allowance, according to my understanding). Anyway, she suggested recutting my squares/triangles an inch or so bigger as they are trimmed to square after the fact anyway. Next time I'll know where/how to check my finished size to get what I need for the background pieces.