I have a 19' cutty cabin outboard that has two 12 gallon tanks boxed in (home made) under pedistal seats that are awkward to say the least. My goal is to configure the deck space as efficently as possible. One suggestion made to me was to bury one large tank under the deck and build storage boxes under the seats. My real question is "Are two tanks safer than one tank?" Knowing Me I wouldn't fill a large tank as often as I would a smaller tank leaving more air than liquid in the tank. Are my concerns valid? Thanks in advance.