I'm planning to make my first wine this weekend and would like to use a 6.5 gallon Carboy for primary fermentation. The instructions recommend a minimum 7.9 gallon bucket. I assume that is just for head space to prevent foam overs like in homebrewing. I always use a blow off tube with my Homebrew because it always foams over. Does anyone know of a reason not to use the Carboy for primary?