On the rail
I recently purchased a C-38 and removed what I and the surveyor considered an unsafe propane installation from the starboard cockpit locker. According to regulation, propane lockers must be sealed to the interior and open to the outside so that even if they leak, the gas can't enter the hull space. After much soul searching, I had two of the tall scuba-looking tanks (aluminum) installed in a plastic locker mounted to the outside of the stern pulpit on the starboard side. The locker protects them completely from weather, any leaks from expansion or whatever flow over the side and the locker isn't any more obtrusive than the Lifesling mounted on the opposite side. The lockers are available from Sure Marine in Seattle. I'm happy to go into more detail, if you're interested.