The cracks were right at the edge of where the hub meets the blade. Since I have the same crack 180 degrees and on the opposite half of the hub of the same blade, I can only think that the blade is a bit out of round. On the blade root I can feel where there is an overlap or seem in the carbon fiber. I see that the hub contacts the blade 360 degrees around but that it does so only about 1/4" deep into the hub then there seems to have been a void for nearly 3/4" with various contact marks within the hub. My cracks are eliptical with a radius of something like a dime. They enter then turn right back around and exit. Within that 1/4" contact mark in the hub. Stress fractures. Possibly could have been avoided I suppose by rotating the blades around of which I never did. I assume that would require another dynamic balance so I left them in their respective ports.