Glad you asked this question. Even after several versions, I've been struggling to get the right chocolate profile in my Milk Chocolate Stout, inspired by Young's. Not looking to clone, but experimenting to determine the impact of different additions, and which ones I prefer.
So, 4 Oz. of nibs in 5 gal. is about twice what I have used. And I have not been roasting the nibs. So, roasting at 300 F for 10 minutes about right?
Is the use of Chocolate extract in addition to the nibs useful? I tried 2 Oz. in my last batch, and could not taste any impact. Maybe that was too little also? Or is this not an effective method to add chocolate flavor?
The only significantly perceptible chocolate contribution, at least from my experience, is adding about 8 oz. unsweetened cocoa at F.O.