I'm thinking that perhaps you are wanting the pinwheel to be unfinished 4.5" and the other sizes to cut to finish at 8" There are instructions for an economy block that size at
https://www.leilagardunia.com/blog/e...block-tutorial That just shows the economy block, but the center is 4.5" unfinished. So I went and found this page that give the size for the center pinwheel center to finish at different sizes, included 4" finished at
https://www.generations-quilt-patter...ilt-block.html