Gulp, that is a challenge, indeed. I can figure out how to make simple blocks bigger but this one.... I was looking at the two larger triangles that are cut from a square. Can you start out with a a square that is 6.5 inches and cut it diagonally? Once the center seam of the block is done, the block should come to 12.5 unfinshed. And then figure out the rest of the measurements from there. For example I was eyeballing the two small squares. One square could be 1/3 of the measurement of the straight side of the largest triangle. Better yet, find someone who has the program for designing your own blocks....think it is called E7?