If you cut a block on the diagonal for the setting triangles, as dunster said you would have bias edges. Also you would lose the points of the star shapes. I don't have a program that I can play with your image to show what I mean. I would think if you could find some white or maybe even tone on tone white for the setting triangles that would be better for setting on point. Perhaps if you printed out the picture of your blocks and then cut the paper across the diagonal and then fold under the 1/4" edge, you might have a better idea of what it would look like.