I have used ... and still own some of ... several Dive Rite configurations. I own and use a TransPac II and a TransPlate. I currently own a Rec Wing. I used to own a Venture Wing. I have dived the Trek Wing. So I can provide some comments based on personal experience.
To answer the poster's original question ... yes, the TransPac II and any suitable wing will replace the jacket style BC. In fact, as soft pack BCD's go, the TransPac II is a very good performer.
What some people are trying to say is that for the same money, a backplate and harness system will produce better durability, performance (a matter of opinion in some circles) and modularity (for upgrading at a later date). Dive Rite makes a backplate system called the TransPlate that is very similar to a TransPac II, but uses a stainless steel backplate instead of the standard denier material. You may want to take a look at it before making your decision. Personally, I own both and prefer the TransPlate.
I don't think the Trek Wing is a good choice if your intent is to eventually use it for doubles. The top of the wing is rather constricting ... even on some larger singles cylinders. You didn't specify a number of things that could help you make a more informed choice of wing ... such as your size and weight, exposure suit, and size of cylinders you plan to dive. These all need to be considered when deciding the appropriate size wing for you.
FWIW - I think the Venture wing is one of Dive Rite's nicest wings ... but it's designed specifically for singles. It only offers 30# of lift, but if that's all you need, it's an excellent choice.
I'm not personally fond of the Trek Wing. It's narrow at the top, wide at the bottom, and tends to be more difficult to vent than some other single-wing designs. If you're looking for lift in the 40-45# range, I'd recommend looking at an Oxycheq or Halcyon wing instead. I use an Oxycheq 45# singles wing, and I think it's one of the nicest pieces of gear I own.
If you need a larger wing, the Rec Wing is adequate for singles with the bungee installed, or for small doubles if you remove the bungee ... but it's not ideal for either. IMO - no one makes a wing that's good for both ... there's just too many compromises involved in accommodating both singles and doubles.
For a singles wing, you want to look for something that's donut shaped, fairly narrow in the center (where your cylinder sits). The donut shape provides a bit of air beneath the bottom of the cylinder that helps stabilize your trim, and it gives the air a space to travel from one side to the other to make it easier to vent.
For a doubles wing, you want something that's horseshoe shaped, and fairly wide in the center (to accommodate two cylinders). The same thing that gives a donut shape advantages for singles proves to be a disadvantage for doubles. And a wide wing that's built to accommodate doubles will "taco" around a single cylinder, trapping air and making it more difficult to vent.
So the bottom line is, use a singles wing for singles, and a doubles wing for doubles ... or accept that any wing you try to use for both will produce compromised performance for either.
Hope this adequately answers your question ...
... Bob (Grateful Diver)
