I'm reaching out on behalf of another brewer friend of mine that has a 15 gallon barrel. He wants to oak a stout and wants to use the 15 gallon barrel but his stout batch is only 5 gallons. What's the verdict.... is it ok to only put 5 gallons into a 15 gallon oak vessel ? isn't there to much head space not to mention the barrel "breaths" so to speak and only the bottom 1/3 would be swelled from the beer and the other 2/3 dry allowing oxygen to fill the head space ? I have little knowledge of barreling so I told him I would ask the more experienced folks here on HBT. thanks for any input.