Looks pretty cool!! You might want to add some kind of support or brackets to hold the cylinder more securely. Maybe a couple tabs and a ratchet strap. Looks like a nice cart.
thats all in the plan. i just have to get the rest of the frame built so that i have a place to attach the upper ring. the bottle will be sliding down inside of a fully sleeved area. its hard to describe but the bottle will be completely enclosed and supported.
