The juxtaposition of loose - to firm - gauge crochet is quite interesting in this shawl. Using a 2:1 ratio of gauge, the stitch count simply doubles by going from the large to the small. This would apply to whatever sized 2:1 ratio hooks you experiment with at home. I love the texture of the very loose gauge in an otherwise tight stitch. However, when you want a lot of detailed stitchwork, like the beautiful floral edging, you need the crisp definition of a finer hook size.