I just finished racking my wine from its primary fermentation bucket to a 1 gallon glass jug. There seems to be a lot of headspace, but my local wine shop (based on what I told them over the phone) thinks this is okay since this off-gassing phase will form a "cap." Hopefully I've attached a picture...if not, in my 1 gallon growler there is about 1.5 inches plus the neck of my bottle. Anyone else have input here??