victorzamora
Contributor
Can't speak to SM, but slinging a bottle without screwing your trim and/or making yourself more accident-prone is simply not that hard. Maybe it's not an OW skill, but it should be covered in AOW -- though I know from experience that many AOW courses just don't cover it.
I don't know if it needs to be covered in AOW, but I know that I've never slung an AL80. I know that, without prior SM experience I would have no idea how to sling an AL80. I know that most BCDs are not conducive to slinging tanks. Most divers don't have a stage reg (or pony reg, or whatever you call it) to dedicate to another tank. Most divers have a hard enough time keeping up with 4 hoses and 3 regs....I'd hate to add the task loading of another tank, 2 more hoses and 2 more regs.
EVEN if many divers have used a slung bottle before, a "bottomless" dive is not one I'd use to gain proficiency at a skill. A diver should enter that dive CONFIDENT in their skills and equipment configuration.