I always hear the 4oz average for most 5 gallon batches. At least that is what I read in Palmers "How To Brew" book.
On Deck - Imperial Stout, American Blond, Amber Mock Bock, "Cricket" #2
Primary - Dunkelweizen, Apfelwein
Bottled - Amber Wheat, Stout, Hefeweizen, Porter, Best Bitter