Recently, I have been toying around with doing an American Rye stout with juniper berries loosely based off of Sierra Nevada's Juniper Black Ale. So I emailed the brewer - I can't remember the exact number he gave me but I do remember that, when converted, it came out to be .73 oz per 6 gallon batch. He also informed me that they added the berries with a small dry-hop addition, and to thuroughly macerate them before putting them in the beer. Whenever I get around to brewing this I will probably just soak that amount of juniper in a couple ounces of vodka for at least a week.
Hope this helps!