I actually got a good weight test on Thursday because I left most of my lead at home and spent most of the dive carrying around rocks. I've had a lot of trouble determining the "minimum amount of air" in my suit, but recently I found that at some point I can't take a full breath or reach my valves, so I've been calling that (well, slightly more) the minimum.
The final verdict was that 20# (incl BP) was okay with a 15L steel in freshwater with just my main (thick) fuzzy undergarments, but if I wore my extra layers I'd need a few more pounds.
I used 18# in salt water with a 12L tank and just fleece, but I'm pretty sure I had about 5# too much (limited selection of bricks)
The final verdict was that 20# (incl BP) was okay with a 15L steel in freshwater with just my main (thick) fuzzy undergarments, but if I wore my extra layers I'd need a few more pounds.
I used 18# in salt water with a 12L tank and just fleece, but I'm pretty sure I had about 5# too much (limited selection of bricks)