Often times, a shop has a bigger profit margin on pre-cuts (less overhead costs). I have purchased various pre-cuts because I like the variety in the package and I like having a pre-cut when I feel the need to just sew something, but I would not waste them on a pattern that required trimming. Just calculate how much fabric you need for your 9" and purchase it. At least the piece leftover from the WOF will be large enough for another project.