I hear "common sense" and I shiver. Common Sense is not Common! I have dove with PADI Instructors who advise to use the Dry Suit for bouyancy control and BC as Backup. I have dove with NAUI instructors they say just the opposite. I have dove with Army and Navy divers that say to just put enough air in the drysuit to prevent squeeze. It seems to some to make sense to put air in the smaller bladder as opposed to a large suit. It is entirely up to you, the diver. The instructor will give you the doctrine, but as we have seen in this discussion, you are going to do what YOU think is best!