Ace,

Keep the trans-pac for single tanks. I have used this for many years, although, I now use a STA (Single Tank Adaptor) with my smallest bladder. That bladder is a Halcyon 40 lbs. Explorer. It is a little too large for single tanks, but I don't dive singles enough (once in 3 years) to warrant another bladder. For doubles, I use the 40 lbs. or 55 lbs. Halcyon Explorer. The bladder choice I make, is a function of the tanks I am diving. With double 95's or 119's I need the additional lift of the 55 lbs. bladder, due to the depth I dive and the additional gear I am carrying. The 40 lbs. bladder is for the lighter doubles I use. As for the "super wing" from DR, sell it. The bungied wing is an entanglement hazard. A bladder should "wrap" around the tank, as opposed to sticking out like the bungied wings do. Unless one intends to dive with a submarine on your back, no one can use all the lift the double bladder promises. If you inflate the double bladder, you will see that both internal bladders can not fully inflate. This is due to the restriction of the external material covering. One bladder or the other can fully inflate, but not both at the same time.

As for the tank issue, proceed with caution. My first thought is, if you intend to start diving doubles, double up a set of lighter tanks. A tank that comes to mind are the HP 80's or 85's. My first set of doubles were a set of steel 72's. With a bad back, I would try "hefting" some one else's doubles. I would not dive a large single tank. That lowers the center of gravity of the tank, lower on your back. This is where most back problems emanate. I too, suffer from back issues, and the "higher" the tank(s) sit on my shoulders, the better I feel. It is the entrance to, and departure from, the boat where all the issues occur, not the diving.

A recommended wing manufacturer would be the Halcyon, Oxycheq, Golem Gear. All these guys make a really good product. They all have developed their wings from YEARS of experience.

That is the short answer to your inquiries.