CuriousMe once bubbled...
I was taught that in salt water an AL80 was 4 lbs negative full and two pounds positive empty...
Note the 6 pound swing. I think it's closer to -3 to +3, either set of numbers is close enough to make a good, educated guess. In any case you've always got to get a nearly empty cylinder and work out your weight in the water in order to be spot on.
newdiverAZ,
You're right, the characteristics are closer to steels; one thing this does is move more weight up over your lungs than a standard AL80 which forces you to put more weight around your waist. So technically you're weighted the same, you just moved where that weight was and this effects your trim (for the better, BTW).
If it looks like you can drop more than the delta in empty buoyancy between the cylinders, you're probably over weighted with the normal AL80s. It's fairly common that people get used to diving with X amount of weight and when they do something to perturb the system they go back to the basics and get properly weighted again, but never challenge the original, "standard" system.
"Neutral" is misleading because by omission Lufxer implies, but of course never states that it's neutral from full to empty (A physical impossibility). Some shops, who as a whole I find very cylinder naive, fall for this and actually tell customers that they don't swing at all from full to empty. Luxfer, of course, stands mute on this in order to sell more cylinders.
The fact that a neutral costs a bundle more than a standard AL80 and you can make a standard AL80 have *exactly* the same buoyancy characteristics by strapping a three pound weight onto the tank strap for 2-3% of the price of a new "Neutral" AL80 makes the neutral a solution in search of a problem.
Roak