That Aerocon valve looks like it is rated properly, although I'd still contact the manufacturer before using it.
This is one of those places where intuition and physics butt heads. Lots of systems meter CO2 -- paint ball guns, airbrushes, even fish tanks. But something as simple as turning the tank over changes the parameters completely.
See, if you have an upright tank -- or a non-siphon tank -- you only get dry gas. That's what most of those cheaper valves are expecting. It also doesn't look like anything. To get that big plume of white smoke, you need to release LIQUID to the atmosphere. That means you are running liquid CO2 through your valve. That means that if and when you get a freeze or other blockage in the system, you are allowing expansion from liquid to gas to occur not inside a tank rated to 3,000 PSI, but inside your plumbing.
(It's a little more complicated than that; as you lower the pressure in an upright tank, some of the liquid becomes gas. That increases the pressure again -- a CO2 tank will stabilize at a pressure dependent on temperature. But this whole balancing act depends on their being a cap of gas, and that you are bleeding off gas, not liquid. Hence the anti-siphon loops on...well, yes, even modern paint marker guns.)
And, yes, you can get away with it for a while. I've seen plenty of paint markers run spitty (usually before they get too cold to shoot at all). But if you are talking about letting out enough liquid for a nice big plume, you are talking enough material to shatter cheaper parts and cause you severe injury.
Please. Do the research, talk to the manufacturers, get help from an engineer -- don't just throw together some eBay valves and a 20lb tank and hope it all works.
Incidentally, I'm not an engineer. Not even a physics geek. Just a very careful theater effects person who reads up on things before putting them in actor's hands.
hehehe
