I'm working on this block now. I'm using a 2 1/2" center square and 1 1/4" side strips. My corner triangles are also 2 1/2" squares cut on the diagonal, rather than larger squares quartered as in your tute.
I have found it easier if I cut off the overlaps of the strips before I sew on corner triangles using the 45 degree lines on my ruler to keep the block square. Will send pics later.