Specifically, how do I alter the weight of a gas, to make it naturally sink to the ground like CO2 does?
EDIT: never mind, I figured it out. Somebody can delete this thread if they want, I can't figure out how (or if) I can do it myself
Every time someone asks a question on the internet and responds to himself with "never mind, I figured it out" without telling other people what the solution is, the internet dies a little. If you wrote down the answer to your question this thread would be useful to other people with the same problem, now it's just a dead end in their search for a solution.
elem.property(elem.[elem.allocate first arg here]_PT_[elem.allocate second arg here], "Gravity", tpt.el.co2.gravity)
"never mind, I figured it out" without saying the solution should be punishable.