I would echo every thing Bama said. If an open circuit set-up is what you yearn for. Look at HP steel tanks. You may be able to get away with a single tank, depending on your anticipated needs. If doubles are in the future, proceed with care. Try not to get drawn into the hype, and continue to look at the smaller, lower profile cylinders. Triples should not be an option with the myriad of higher volume tanks on the market.