You need to be careful with the propane bottles. A one pound bottle has enough gas in it to blow the deck off a boat. If you dont have a propane locker on your boat there are a couple of other options.
I think Magma sells a canvas bag that is designed to hand on your life
lines and provide safe above deck storage. It holds three or 4 bottles. Make sure you position it where the gas would flow overboard (not into the cabin) if you had one leak. If you choose this option and dont go through the bottles very fast I would suggest that you seal the spare ones in heat sealed bags (like the ones used for sealing food for boiling). That way they dont rust.
Another way I have seen people store the bottles is inside a large diameter piece of PVC pipe that can be held to a life
line stanchon with hose clamps. Im not sure how they get the bottom ones out. Maybe they have an l shaped lifter that goes to the bottom. That could be made from pvc too.
Before I took off for a race to Hawaii a few years ago I was required to have my boat surveyed. I hired a man who had just completed a circumnavigation. He found the little propane refiller for my gas
grill lighter in a drawer below deck and told me, on no uncertain terms, that I should be storing that above decks. If that little bottle is dangerous, then the one pound ones are really dangerous.
Also, be especially careful of the bottles that are half used. If you remove the regulator they somtimes leak. you can heard it if you put the bottle to your ear. The rubber seal is supposed to close the bottle but if there was rust or other dirt on the bottle when you installed the regulator it can keep the seal from forming.