If you can expand a 4 bight to a 6 bight you should be able to increase a 6 to a 8 or a 10, 12, 14...
It just gets a little harder to keep track of where you are at. I never could really adapt to different sizes of the same knot until the little light went on inside my head and I understood what I was doing vs following a cook book. I am afraid that might not be as much help as you want but if that light comes on you will get it no problem.
Mike