What would you do?

[AfterDark]

Oh, I totally agree that doing this dive on a single tank is not at all advisable! I'd do it on doubles, with a deco bottle; but then again, I want more than 10 minutes of bottom time, and I don't like cutting anything very fine with respect to gas.

The emergency consumption rate I was taught was 1 cf/min, doubled for two divers. As I said, I don't do metric. The OP made it clear that he would not be going into much, if any, mandatory deco.

There's no doubt this dive (like all IMO) is one that should be done on one's own terms and planning, and with ones own gear if possible. Under no circumstances would I do this or any other dive that I didn't feel comfortable with and certainly not if someone else is going to dictate how much air/gas I need!?! If a diver isn't capable of planning a dive like this on their own, well that's red flag #1 isn't it? If someone else is doing the planning then BIG red flag and game over.