Bonjour,
John, don't worry, your problem can have simpler solution
Personnally, I like using large gas tanks as they are supposed to freeze less than the small ones.
Because of this choice, I ALWAYS test my boats in my bathtub or on table if too long, boiler full, machine operating without stopping (except for a gas regulator test) at middle throttle and playing with the whistle to time the time it takes for the boiler to empty, which means water is at the lower level of the boiler which is not empty so.
Then, on the pond, i always check my navigation time with my stopwatch.
Why am I fully confident with my method ? At first because it is very difficult for our torchs or ceramic burners to heat until debrasing a boiler especially when a little steam remains in the boiler. Furthermore, I have ragulators and RC safety gas valves in case of big problem like propeller blocked by a piece of wood for example (lived experience).