It's a weird bit of math in why seam allowances on the diagonal are not what you might think. Remember that triangles have their own study -- Trigonometry. The short (quilting) form is that when you are cutting diagonals, the formula is +7/8ths for the point, not the 1/4 for the square side.
I wouldn't cut the blocks for a number of reasons. BTW, love the blocks you are working with, looks like you are doing excellent work! I would use white? that forms the linking pattern or something with a white base (like the center squares) for the setting triangles. That would make the whole design sort of float.