Welcome from Ontario, Canada. If your 9 patch blocks only need a slight trim then you can do so without distorting the blocks too much. If you have more than a little to trim off, the blocks will become smaller on the outside than the center block. In this case you can either just go with the distorted but squared blocks or turn them into another pattern where the size difference would be less noticeable like ......Disappearing 9 Patch. There is a tutorial on Quilting Board I think?