This shop owner is so full of crap that it's spewing from his mouth. I require my aow students to sling a 30 or 40 cu ft stage. They are trained in its use on the first dive. Deep course? 95 cu ft tank minimum, 30 or 40 cu ft stage, doubles, or sidemount. To have you do a deep course without a redundant air supply is reckless, irresponsible, and dangerous in my opinion. Making you do 50 degree water in anything less than a 7 mil or drysuit is damn near criminal. You need to warn people about this shop. They are going to get somebody killed.