Those of you who haven't used one, don't knock it! The USD Aqualung II was a first rate BC in its day. A minor modification gave it the same ease of inflation as the today's jacket BCs.
All you had to do was remove and toss the CO2 cart and its fitting. Replace the cart fitting with one that accepts the LP hose and a valve that enables you to have inflation control.
I dove with one for many years, from the late 70s into the 90s. Then I got careless one day while cleaning a badly barnacled boat bottom (love that alliteration) and damaged the bladder. Couldn't find a glue that would stick to the bladder material so I wasn't able to attach a patch. No replacement bladder could be found, so I had to switch to a jacket style BC.
As I recall, the II had a lot of lift, somewhere beween 35 and 50 pounds.
The modern day jacket style BC is OK, I guess. But I miss the ability to ditch everything, tank, weights, etc., and still have my BC.
Warren