the trick is you want the small bottles really cold and you want the big tank warm
so winter time small bottles outside and bring big tank inside to warm up before you do it
summer time big tank outside and bottles in freezer before filling them
big tank upside down and you are best to fill them twice
fill then let them stand for 10 minutes in the cold and refill
it is possible to over fill but no worry of them exploding as they would need a lot more pressure then that to explode..but if they are completely filled with liquid propane they will spit out liquid, not gas so the heater will not work right..if that happens just let a bit squirt out...
don't do it in a fish hut, because when you do get it to light the hut will lift off the ground..at that point knuckle hair and eyebrows will be optional ...
after a few of years of use some valves do stick open and the propane will all leak out of the 1lb bottle..(if you take good care of them and put the black caps back on them between uses this may not happen..I don't)
you can screw it onto the heater to stop it or have a blowtorch ready to screw onto it to stop the leaking......once you use a leaking valve bottle throw it out
I have had 2 do it in the last 3 years...no big deal