The Polaris II uses a non-balanced piston first stage. The vast majority of examples have a single LP port. An additional LP port was added during the late 1970s.
The second stage is the standard unit used on the majority of Voit regs from 1969 on. A modern Mares Abyss diaphragm (available from VDH) improves the performance considerably.
The second stage needs to be adjusted with a cylinder pressure of 2,400. The IP will drop 8-10psi from 2,400-500psi. I suggest setting the IP between 124-140psi on a full cylinder.
Breathing performance is perfectly adequate for dives in the recreational range.
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