If I do everything just right, prewash, cut accurately, nice 1/4" seams, etc, I will still be off. No matter what I can't cut 4 5" squares and come up with a nice pretty 9" square. And it's hard to square up when it's less than 9" (which it often is, even if I over cut). It's one of my biggest frustrations. Some of my points are picture perfect, while others are a big fail. Flying geese are my big downfall. If the seams are too far off I'll redo but I have no hard and fast rules such as 1/8" gets a redo. In the end when it's washed and wrinkly the overall effect really isn't that bad and it usually looks pretty darn good. And unless I'm entering a contest no one should be looking that closely.