robrub has co2 tanks, but they aren't powertanks... he uses the industrial welding i think tanks... he has a powerflow regulator. hes got a steel tank and an aluminum tank, both are quite heavy though, i think his are 20 pounder, i think he got them pretty cheap, a lot cheaper than a powertank, he does use a power tank regulator though
the only drawback is there isn't a handle/gauge protector with his setup like the powertanks have