Wow.......I understand this was a paniced diver, but he blew through 800 PSI at 65- feet in 30 seconds, that's a lot of gas. Then he sucked down your HP120 @ 1400 PSI so you both had zero............more gas! You had your hands full with a diver who should have never been solo diving in the first place (and I like to solo dive). I normally grab an OOA diver by the BC and try to control them in an acsent, venting his BC and looking into his eyes, trying to calm him, if you can. They will never think to do these tasks, they only want to get to the surface.
So he used 80 cu ft, plus your gas in fifteen minutes at 3 atm........outrageous.
Pony bottles are really the answer. But I must think, he would have sucked down my 30 in these conditions really quick. I always carry my 30, and doubles too, so I take plenty of gas.
I'm glad you guys are OK, and you managed this problem as efficently as you could.
I think your onto something. He didn't need a pony, he needed more gas. Could have been a pony, could have been doubles, could have been more air in his single.
I like and use a pony but it's a smaller one based on my gas consumption. This other guy would have probably sucked it dry before he got to the surface.
I know you should always plan to have gas to get you and your buddy to the surface but it sounds pretty tough to plan for a random buddy that needs that much air to come out of nowhere when your near the end of your solo dive.