Another casualty of converting a CNG stove to propane is the lack of thermocouple valves. These switches will sense if the burner flame goes off and will shut down the gas supply. They are used in propane systems as most stoves are installed inside the cabin. Having said that, years ago before trying to idiot proof the boats, a propane system just consisted of the basics, a tank, a regulator, a supply hose and the stove. Yes it was inconvenient to turn the tank valve On and Off every time the stove was used and it was also inconvenient to have to stand and watch the flames when the stove was on but it was considered normal. Now they want to leave the tank valve open all the time and be able to start cooking and walk away to do other things. These safety items are all about convenience and not having to be responsible for teaching safety. The aesthetics of having a 20 lbs tank on deck or over the rail were not the best but as long as we could have hot food we did not care. At one early point we had a supply line made of copper tubing but I guess using our nose as a sniffer and keeping the tank valve closed mitigated the risks. Yes CNG as a fuel for portable tanks will disappear shortly (not the fuel, but the filling stations, the filling equipment, the tanks, all as a result of dwindling demand) so start planning your move to propane. The transition could be done all at once or piecemeal.