I'm another that goes one inch from finished size on hst's. No matter how accurately I think I cut or sew, I always have issues. The 'correct' measurement is 7/8" added to the finished size of your hst. I prefer to have that 1/8" to play with and then square up using the 45 deg. line on my ruler. And if you're doing lots of them (I seem to love patterns with hst's) invest in a rotating cutting mat. OMG what a lifesaver! I've used 'Thangles' and they are ok for me, but I prefer my method. I've seen Jan's method in some patten books but have not been brave enough to tackle that. But it looks like it would be far less wasteful. But I'm scared!