Agreed with the two above- Extra Light extract all the way. It may well have been Yooper who showed me the light on that one a few years ago, and my beers got a lot better real fast. I would drop the black patent if I were you, and maybe add the 2 oz. back as roasted malt, which is delicious. I personally like the complexity of the chocolate malt in this beer, but you could also, as rjwhite suggests, sub it out for more roasted as well. Roasted malt is the only dark grain in Guiness, if you need a flavor reference, though with your crystal malt, your beer will have a rounder, sweeter flavor (which I for one prefer to Guiness). A big roasted malt flavor is my favorite thing about a stout.