You won't get a 12" block doing a D9P unless you cut odd size squares (4.666"). Cutting 4.5" squares will get you a 11.5" finished block, 5" squares will get you a 13" finished block. Just plan to adjust the rest of the quilt accordingly. Enlarge/reduce borders to get the overall size you want. There's no rule that the blocks HAVE to always be 12".
D9P looks great with sashing too. I finished this top recently.
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