"The AIR 2 is a solution in search of a problem!" You read that all the time on the boards, but for some of us it was quite the contrary. Forgive me if I get a few timeline details mixed up, but in the early seventies we learned to dive before the BC, power inflator, and octopus were "required" pieces of equipment. In my Basic Open Water class we had pressure gauges, but the moss backs in the dive club I joined still had a J valve or an SPG rule, but I digress.
So how did the AIR 2 fit into my scuba equipment evolution? Well, around the time the AIR 2 was introduced (late seventies) not all regulators in service had more than two lp ports. In fact some only had one. My Dacor Olympic had 1 hp and two lp ports and there were plenty of other regulators outfitted similarly. When the "industry" started pushing buoyancy compensators, power inflators, then a safe second/octopus on us, we had to attach multi-port swivels to satisfy those requirements. But ScubaPro came out with a unique solution-the inflator regulator. It made a lot more sense to many of us who learned buddy breathing in Basic Open Water. Give up (and not have to share) your primary and breathe off the secondary. It had the added advantage of a regulator you could take a drag from, then exhaled air directly into the BC just as we did before power inflators.
So the AIR 2 was a solution to a solution in search of a problem.
I still use one, albeit a 3rd generation. If you decide to incorporate one into your system, don't forget you'll be donating your primary, so a longer primary hose is necessary. I've also found using the correct length corrugated hose and a Myflex regulator hose with an AIR 2 quick disconnect coupling makes the "can't turn your head" complaint a non-issue.
YMMV,
Couv