Originally I was keeping my 3 gallon portable gas tank in the cockpit under foot where everyone else keeps it. When I was going to be out for a while I would close the vent and make sure the cap was on tight then stow it in a compartment in the back of the boat where I keep my extra anchor, rope and other bulk items that get in the way. Eventually I found the space it was occupying in the cockpit is a perfect place to keep a cooler so I decided to keep my fuel tank in the compartment and just open/close the vent as needed for running the outboard. I would consider this to be below deck although it is not directly connected to the cabin. This space is also vented and at no time over the last 2 years have I smelled any fumes in the cabin or back in the compartment. This year I plan to replace the 3 gallon with a 12 gallon so it only needs to be filled up once a season. I am a fair weather, day sailor on lake Erie and run the motor for 5 minuets or less before I'm in open water with the sails up. The boat is a 26 ft fractional sloop with a swing keel. I would like your opinion if you think I'm going to blow myself up.