You guys really need to take a look at some HPA systems, commonly found in use in paintball guns. They are small 68cubic inch fiberglass/epoxy wrapped cylinders with integrated regulators. They can hold up to 4500psi currently, and output as little as 300psi. Using one of these to inflate a mast bag would be simple. I would know, I used mine one time to blow up an inflatable chair. Lets just say "blow up" is the appropriate term.