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It doesn't affect the filling if your using flame king refill tanks.I broke mine off before I got the actual refills from them because I used to refill the disposable tanks.the flame king refill tanks work just fine.I fill mine up, close the vent screw when gas starts coming out (as per the instructions), then I close vent screw just let if fill up the rest of the way. I end up with close to 2lbs of propane per tank. I am not too concerned about pressure, the flame king tanks are pretty stout and I checked the release valve, there is not too much pressure in tank after filling it that way.This is NOT the way you are instructed to refill the Flame King tanks so proceed at your own risk.
Does your 2lbs include the weight of the tank, or is that the amount of propane? I could see a few onces more, but double capacity seems like a lot based solely on volume limitations.
I question your math .a gallon of propane weights 4.24 pounds,a 1 pound cylinder holds a quarter gallonmaximum amount of propane in a one pounder no matter how you slice it is 1.06 pounds
If I remember correctly the FK tank empty 1.8 lbs ..after proper refilling its 2.8 . I think I burned more propane this season then in the past 10 yrs combined . Since getting the FK refillable tanks I no longer worry about the use of propane. If I get cold crank up the heat in my Portable Buddy in my uninsulated two-man Frabill . One of the best investments I have made .