I don't think you should ever carry a pony or dive double just so you will have extra gas if you need it. When you did OW you should have been taught 2 urgent ascents. Controlled swimming ascent and emergency bouyant ascent. If you plan your dives, use gas management and carry redundant equipment how will you ever get to use all of the skills taught in OW. I mean seriously folks, we all use mask clearing, reg retrival and neutral bouyancy but come on now. How many of us have ever done a good old fashioned blow and go, or even a controlled swimming ascent for that matter. Are we all failures as divers? :fail: We all ought to hold our heads in shame:depressed: and apologize to our OW and AOW instructors for not using every skill taught us. I am on the phone now to call my first instructor and apologize :crying2: for not having done the emergency ascents to consider myself skilled at them.
:focus: I only carry a pony as a bailout, and it's got plenty of gas to let me ascend at a normal pace and still do a safety stop. It's kinda like my octo, if I'm using it, I'm on my way up.