texdiveguy:I lost you on, "I don't think I can plan for OOA." I am not understanding that satement??
A 30cf. would be plenty of emg. reserve gas.
I'm saying there are situation such as equipment failure or my buddy OOA, that I can't plan for. I don't plan dives with pony in mind. I think the choice is coming down to 30 or 40. I'll check the price and compare them at my shop. Hopefully, they give me a good deal.