I know that the general rule is to cut your squares 7/8" of an inch larger than than the desired size. I always cut mine 1" larger and trim them down. Extra work? Yes! But I never lose a point that way! For trimming down, I went to a local glass shop and had squares of plexiglass cut for the size of my blocks - 4 1/2", 5 1/2", 6 1/2", etc. couple of bucks each. I measure them before I leave the shop to make sure they are square and the right dimensions. When I get home. I draw a diagonal line on one side. I then cover that side with Invisigrip to prevent the diagonal line from being rubbed off and prevents the square from shifting on my blocks. I lay the diagonal line on the ruler on the seam of the HST. I then trim them. It keeps my seam in the center and I'm not trimming a lot off each side of my block. I also use a rotating mat. Makes easy work of it but it can be tedious, depending on how many HST are in your project. The extra work is worth it to me if it means perfect points everytime!