I'm working on my first DP9 and LOVE the pattern. Mine is done using the same fabric in the corners and the same fabric in the center. The rest is mixed. I think that using the same fabric in the center is a good idea. I don't know if black might not be too harsh because I don't know how dark your fabric selection is. At 9" you could do 4.5" squares to get the most bang for your buck. Personally, I like the scrappy look but I do like it when the corner squares are standing out a bit.