I'm persuaded that for the most common flavors of rec diving there is usually a better alternative than a pony, but I'm not going to attempt to persuade anyone else. Go on, sling that thing!You GUE guys need to come to terms that people are going to continue to use pony bottles for redundancy. It is a perfectly valid configuration for recreational diving. Just let it go.
Indeed, in post #2 I commended the OP for at least appearing to have thought through the gas usage estimate, which some pony-slingers likely don't.