Just purchased a Zeagle Concept BC (not Concept II). I really like how it fits. Buoyancy is 24# (is this enough...5'4" 140 3/2mm suit). My question is this BC has a soft back where the tank attaches. Is a hard plastic attachment or the soft back like the one I purchased better. I have yet to dive in mine and am asking so if this was a poor purchase I can still return it for a full refund. I plan to do predominantly warm water diving (going for Nitrox and AOW this month) and maybe wreck diving in the Great Lakes (water is cold). Will this be enough BC for me? Does the tank flop around with a soft back? Anyone use this BC and like/dislike it? Thanks ahead of time.