Do you actually see people diving with pony bottles?

[Wookie]

Not arguing that. Just saying that such rules don't suit me, so I won't use those boats.

Exactly (and I'm not being snotty), there is a boat suited for every diver, and some divers prefer certain boats. And if for whatever reason you don't like the boat, you and the boat will be much happier if y'all avoid each other. No captain wants an unhappy customer.

 

[uncfnp]

Most of this week in Cozumel Mexico.

 

[woodcarver]

Yes, I've seen a number of pony bottles used, all in warm water and not just mine. For me it is strictly for the "Oh, s#%&" moment. Since we don't exceed ndl, and don't spend much time at or under 100fsw, and I have to take them on an airplane, they are small. She's carrying a SpareAir 3cu, I've got an H2O EAS on a 6cu. This will get us to, or at least very close to, the surface from 90fsw at a safe rate based on our sac rates x2. I would rather do a CESA from 10 or 15 ft than 60 to 80.
They go with us regardless of depth planned. I like redundancy; still have an SPG w/ depth guage on the regs and a watch on as well as the AI computer. A slung pony, even a small one, is better than no air. She does a better job than I do at being a good buddy, but sometimes we're both looking at something besides each other; that would probably be when Murphy decides to show up. I'd rather go up on her octo, but this gives us another option.
If I could get her to lose a couple more pairs of shoes and some other stuff that never gets used, the 13cu bottle would fit in the suitcase....