First the ground rules
I am talking about general recreational diving, using single tanks and no penetration.
Ok in an ideal world you are diving with an experienced buddy you are familiar with and who wont run out of air and if he/she did, then they know what to do, but what if some inexperienced diver finds you closer than his buddy when the unexpected happens
IMHO
Forth place conventional set up two regs with standard length hoses, one in your mouth and one in the magic triangle zone. This seems the worst configuration but the one most divers use. The other diver is out of air and maybe hasnt attracted your attention in time, he swims towards you and sees a reg in your mouth, the spare is probably stuck in a pocket out of the way, or with the mouth piece stuffed into one of those red ball things or somewhere else where it wont dangle, and / or possible full of sand or other such. His first choice is going to be the one in your mouth leaving you to find the afore mentioned spare.
Plusses easy to swap regs sets around
Third Place DIR - main reg on a long hose up your body and round your neck, spare on a necklace. Same situation as above diver comes at you grabs the one in your mouth, you can easily find the spare, but find yourself either strung up nicely with reg hose round your neck like a nose, or looking at the fins of a panicked diver heading to the surface on the end of 7ft of hose.
Plusses low entanglement / dragging items
Second place main reg in your mouth, spare reg on the inflator AIR2 / Octo+ style. Diver panics grabs your main reg, you reach out with left hand to the inflator that is always where it is, and stick it in your mouth. The other diver is still close so you can get control of him.
Plusses less hoses = less clutter and risk of dangling equipment.
also being an inflator means this piece of kit is regularly used, I use mine most dives to inflate my SMB.
Minus it is always attached to BCD so may suffer damage from being thrown around. (Lower reliability mine has been working for 6 years without problem, its not an issue)
First place complete redundant tank and reg system.
Other things to consider - 2nd stage failure, what is there to fail, the worst should be a free flow, which you can still breath from. So unless your buddy is out of air your spare reg should not be required by you. It is more likely that a 1st stage would fail, in which case both your 2nd stage regs are dead
Opinion / Flames please!
I am talking about general recreational diving, using single tanks and no penetration.
Ok in an ideal world you are diving with an experienced buddy you are familiar with and who wont run out of air and if he/she did, then they know what to do, but what if some inexperienced diver finds you closer than his buddy when the unexpected happens
IMHO
Forth place conventional set up two regs with standard length hoses, one in your mouth and one in the magic triangle zone. This seems the worst configuration but the one most divers use. The other diver is out of air and maybe hasnt attracted your attention in time, he swims towards you and sees a reg in your mouth, the spare is probably stuck in a pocket out of the way, or with the mouth piece stuffed into one of those red ball things or somewhere else where it wont dangle, and / or possible full of sand or other such. His first choice is going to be the one in your mouth leaving you to find the afore mentioned spare.
Plusses easy to swap regs sets around
Third Place DIR - main reg on a long hose up your body and round your neck, spare on a necklace. Same situation as above diver comes at you grabs the one in your mouth, you can easily find the spare, but find yourself either strung up nicely with reg hose round your neck like a nose, or looking at the fins of a panicked diver heading to the surface on the end of 7ft of hose.
Plusses low entanglement / dragging items
Second place main reg in your mouth, spare reg on the inflator AIR2 / Octo+ style. Diver panics grabs your main reg, you reach out with left hand to the inflator that is always where it is, and stick it in your mouth. The other diver is still close so you can get control of him.
Plusses less hoses = less clutter and risk of dangling equipment.
also being an inflator means this piece of kit is regularly used, I use mine most dives to inflate my SMB.
Minus it is always attached to BCD so may suffer damage from being thrown around. (Lower reliability mine has been working for 6 years without problem, its not an issue)
First place complete redundant tank and reg system.
Other things to consider - 2nd stage failure, what is there to fail, the worst should be a free flow, which you can still breath from. So unless your buddy is out of air your spare reg should not be required by you. It is more likely that a 1st stage would fail, in which case both your 2nd stage regs are dead
Opinion / Flames please!