DavidB:Today I dive with a 2 pieces 5mm semidry wetsuit, most of my dives till now was with steel tanks but now i am slowly transiting to doubles, as for their buoyancy I am not yet sure what it is! My BC today is a Zeagle 911 with a single blader of 65lbs. In winter with a full wetsuit today I use 12 to 16 pounds of weight with a steel tank that has negative buoyancy full or empty.
I might tend to offer a different perpsective from a couple of other posters, in that I would suggest a SS BP rather than AL. Yes, you mention transitioning to doubles, but if you dive in winter with a steel single, and 5mm of neoprene, AND use 12-16 lbs, I would seriously consider SS instead. It is just more versatile. I still dive a SS with steel 120 doubles and my wetsuit, but I also use it for the doubles with a wetsuit. Yes, I am negative but it works fine. In contrast, an AL may still require you to use weight (and I hate carrying extra weight on a belt) with thick neoprene and a single. Just a thought.
Just curious, but any particular reason for a 65lb inflation BC? The 911 is a great BC, of course. Are you routinely carrying lots of (negative) gear when you use it?