I like enough quilting to keep things together if washed a lot, but not so much as to be stiff. If the quilt was mine, I would stop with what you've done. I know it's just me but I don't particularly like the SITD method. I like my quilts to be used with either side up and I don't like to see each block outlined on the back, competing with my good quilting. I don't piece my backs unless I use it as a design element. I almost always use a quilting thread that will stand out, especially if the fabric is kind of plain. This really makes a double sided quilt. Ironically, some people I have gifted quilts to prefer the back, because it appeals to them more. Whatever works! Just please use my quilts.