BC and tank for cold waters

[OldWetDog]

I’m 5’7” and dive a HP100 steel tank with a drysuit in Puget Sound. I wear a combination of weights (distributed between BC ditchable pockets, trim pockets and weight belt—allowing me to ditch 6 lbs or up to 18 lbs as needdd) totaling 26lbs. I use a Mares Bolt back inflate BCD and find this setup works well for me.

 

[Bob DBF]

you mean wing/bp is more negative than jacket bcd?

The jacket I replaced had +6# of buoyancy with an empty bladder, the BP/W is -5#. So 6#, or whatever your jacket is, removes that amount of lead altogether, and the BP/W weight replaces some lead and moves it to your back. I removed 11# of lead from my belt, although 5# was just relocated.

 

[Royan]

Hi, thanks for your useful inputs. I've recently got the singles BP/W package from DGX, SS backplate, and tried it along with a very small high pressure steel tank last weekend. No markings in the tank could tell the capacity, but I think it was about 9 liter. DS filled it with 240bar/3500psi.
I dropped 6kg/13lb lead weight from the pockets I used with the jacket BCD (and AL80 tank). It is normal for me to forget a "detail" when I do a big change in my equipment, and this time was not the exception. I forgot to fully close my drysuit zip so I got flooded in the moment I jumped off the boat . I kept buoyancy control all dive long, though I think the flood event helped with that.
Next dive, my undersuit was still in the tumble dryer so the DS owner lend me his Bare SB Mid Layer, and I added 1kg/2lb. Underwater I was good with a total of 9kg/20lb of lead weights. The tiny steel tank was very up in my back, and I was head heavy. Even that, I loved the wide adjustment range of the two DGX cam bands, the long wing barely touch the ground when inflated and standing upright in the boat or the DS deck. That was my only concern about this narrow, long wing from DGX, so I think it passed the test
I have not tried an HP100 tank yet, steel tanks in Chile are rare and expensive, but at least the switch from a jacket to a BP/W was totally succsessful. Now I can't think how I dove 8 years with a jacket style bcd. They could teach this in the first dive course.
About tank gas capacity, dives in Chile are short, usually 30min, and I have good air consumption. While I don't "need" more air, I like to dive deep and longer, and if I'm going to spend money in my own scuba tank, I would like to carry more air just for safety.