Do not add 4 oz! I recently brewed a Rogue Hazelnut Brown clone and added about 3oz of natural hazelnut extract which was overkill. The nut flavor is finally starting to subside and the beer is coming through, but for about a month all I could taste was hazelnut. I suggest adding 1-2oz at first, then taste and step it up if desired. The key is start small, you can always add more. If I were to do it again I'd probably use 1.5-2oz.