sourdough with oats, stout, cheddar, and onion

For my second sourdough loaf I tried this awesome recipe:

http://www.thefreshloaf.com/node/59838/stout-and-2year-old-white-cheddar-sourdough-oats

I followed it pretty exactly, but added caramelized onions and 1/4 tsp instant yeast. I still want to work on getting a slightly better oven spring and more open crumb, but it tasted amazing! I'm still trying to figure out if I am over proofing, under proofing, or not developing the gluten enough.