I play competitive paintball, and only now, as i am preparing for the Ambush Reflex Tournament, do i realize what paintball hpa tanks can do for scuba. How they work is that they have a thin (o.5cm) wall of aluminum on the inside, and the same thickness in tightly-wrapped carbon fibre. They can hold up to 5000 psi (the average scuba tank holds about 3000) and the are extremly light due to the materials they're made of. Because of this, you could have a light, small and easily portable tank that can hold a lot of air. The only drawback is the price; a 5000 psi 88ci tank is about 300 usd, but they include a high quality regulator, and im sure the price wouldnt increase that much as the size increases, becuase the materials are relativly cheap. any thoughts?