On a previous thread, somebody suggested using a little fish scale to weigh a propane tank to see how much gas remains. That sounds like a good idea, except I'd have to know what the tank should weigh full and empty. From what I gather, the tank I need weights 10.2 lbs. full. It's a 2 gallon tank, and propane weighs 4.2 lbs. per gallon (according to wikipidia). Does this mean that there should be 8.4 lbs. in the tank when full, or is there moer than 2 gallons of propane in it, since I assume it's under compression? Anybody have an answer?