What batting are you using? The batting dictates how close together you need to quilt. The batting that allows you to quilt the farthest apart is Warm and Natural (quilting lines up to 10" apart); however, it is a relatively heavy batting and its initial drape is relatively stiff (it does soften up with multiple washings). The batting I would choose for this type of quilt would probably be Hobbs polydown just because it is so soft. I believe quilting lines should be about 6" apart (or closer, of course) for this batting.