Does the type of fermentation vessel matter. Specifically in regards to headspace. I am using a Coopers plastic bucket for my 5 gal. batch. Fermentation is going along nicely, I can see it clearly through the see through lid. There is a lot of head space between the wort and the airlock. I doubt if it will ever bubble out. Is this good, bad, or indifferent as far as displacing 02 or C02.