I'm in the middle of my first patio project using presquared bluestone. The stones are 12x12, 12x18, and 18x18. The actual measurements are 1/2" shorter. I'm finding that most of the 12x12 are out of square, by about a quarter inch or so, as are a few of the 12x18's, a few of which are a bit long as well. Is this normal for presquared or should I bring this to the attention of my supplier. I don't want to complain if this is normal, but if it isn't, I'm paying way to much per sq. ft. to have to deal with this.