That is my favorite placement for the D9P, but I've also used the placement where all blocks are arranged so that they sliced squares form the sashing and cornerstones.
No sashing...you would lose points of interest. I think borders are the way to go to finish off or to make it bigger. I really like this pattern/fabric you used.
I think it's unanimous... : ) It looks wonderful just as it is and a nice border or two would really set it off beautifully.
Please post when you have it finished.