My most recent dives were with 2400psi, 80 cu.ft. steel tanks. Prior to that I had been diving with rented aluminum tanks. I'd expected to be able to drop some weight from the belt due to the negative buoyancy of the steel tank. Whereas I had been diving with 24 pounds with the AL tanks and seemed a bit underweighted still, I went to 20 pounds with the steel tank. The 6 pounds of negative buoyancy from the steel tank would then put me at 26 pounds total.
I found that I was still underweighted however. I could get off the surface only by dropping my nose and kicking. If I then came to a depth of 20 feet or less I popped to the surface like a cork (with no air in the BC).
On the second dive I went to 24 pounds of weight, which was only marginally better. On the third dive I went to 28 pounds and at that point I was overweighted, but I'd prefer to control my buoyancy by adding air to the BC than to have an uncontrolled ascent. With 28 pounds I was able to execute the 15 foot safety stop.
I'm purchasing my own BC so that I can determine precisely what weight I need for neutral buoyancy at the surface with either AL or steel tanks. I can rent tanks for awhile, but for now I want to own my own BC. An integrated weight system will be a nice covenience as well.