You can run a Phoenix or a Royal IP between 140 and 150 with no issues. Frankly, I never carry an octo or pony with my double hoses. Unless some charter operation requires one leave it home. This backup stuff is way over blown. I'm with Pesky, I too have been diving 50 years without ever using or needing a backup reg.
I fully agree, when I rig an octopus it is not for redundancy because an octopus rig really does not provide redundancy, it is there for me to give to a buddy in an OOA situation, it is not there for redundancy and provide essentially none.
I carry a pony sometimes for deep solo for idiot proofing (me). The other time I find them useful is for deep single tank diving as a means of providing air to an OOA diver without compromising my own supply. Example, my three trips recently to the Mighty O. Dove mostly with strangers, my first trip I observed that the depth and size of the wreck and the current was really to much for a typical single 80 diver and yet I bet 90% of the dives there are on an 80. I figured having a pony I could hand off would be useful after one captain complained to me that it had become routine to bring OOA divers up from over 100 feet on this wreck.
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