Have made several centers and then different stages of progress. After several test attempts I settled upon using two crochet hooks ... an I (5.5MM) for the flower and center, then size G (4.25MM) for the remainder of the square.
Its a wonderful pattern and I think will be a well treasured blanket. I still have the blue one in mind too for a very special friend. Once I determine the shades of blue and yellow center I will pack a take along bag for the blue one. I can see that as a Barnes & Noble crochet on those hot and steamy summer days. Hook, yarn and a Java Chip, now that's a summer delight.
Enjoy the weekend.