IMHO (in my humble opinion) a one gallon fermentor is only good for fermenting three-quarters of a gallon at most...my initial thought is for you to give it back and go buy something bigger...3/4 of a gallon, after fermentation and trub removal may give you a 6-pack of beer if you are lucky... jmho...(just my humble opinion)...Now if you were content on brewing a mead I would say differently, but that would involve honey, not barley....cheers!!