I think it just needs more FMQ. I can't really tell from the picture; where all is the quilting design? Is it just through the middle of the rectangular pieces? Or just in the sashing? How far apart are your quilting lines?
If it were me and I were considering SID, I would defnitely do SID only with a serpentine stitch -- much easier on the nerves.
Really, as far as I can tell, it just needs denser FMQ.