FWSY Walnut Levain

I got a copy of FWSY a few weeks ago and this was my first attempt at making a levain. My previous 3 efforts all used biga or poolish pre-ferment. I stuck to the recipe, but reduced the proof times somewhat given recommendations on this site and the temperature of my apartment (about 82 degrees). I also used about 75 degree water instead of the 90 degrees recommended since my home was warm. I also reduced the amount of instant yeast from the recommended 1/2 tsp to 1/4 tsp and increased the amount of whole wheat flour to 20% of the total flour used. I am very happy with how these turned out for a first attempt using my starter! I think the crumb is pretty good, but should I have expected it to be more open?