Since I am a visual person, I started playing around with the pieces and pattern. I like PP better, so I enlarged the little corner piece by 400%. That gave me a finished block at 6 3/8" adding your 1/4" seam would make it 6 7/8" I believe.
It takes four blocks to make up the first picture.
Be very careful about placement of the #'s 4 and 5 as they overlap. I'm going to go to the machine and play with this one. Looks intriguing.