I've got one, thinking of using it

 

I've got a couple of them. But I just use them as storage tanks. I've talked to a few guys that have tried 20 lbers and they all said they got surging, probably due to pressure drop. Maybe if you had a heater designed for that size cylinder it would work.
Again this is just hear say.

 

thanks for the info, probably just go with a 10 pounder