Yes, they work great!

Am I the only one who vents their gas cans?

Amazon.com: 10 Pack Universal Large Yellow Fuel Gas Can Vent Caps Chilton Briggs Rotopax Gott: Garden & Outdoor

In the event of a rollover I'd be more concerned about the amount of bourbon flooding the cabin than the gas on top.

My marine can vents through the cap. Works pretty well if I only fill to the recommended level.

Here is how I have mine mounted. These are 2 of the 3.5 gallon fuelpax. When they are mounted on the top, they expand like a pregnant woman. Venting is a pain as I have to try and spin the rotopax mount to get them undone as they have to be vertical so that the screw cap can be loosened to vent them.

I am still trying to figure out how to hand this. I will be watching to see what you all come up with.

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I recently used two Scepter low profile 3 gallon marine fuel tank that I modified for a trip to Big Bend Ranch. EPA regulations do not allow marine fuel tanks to vent pressure (fuel vapor emissions) so you must modify the cap by cutting a small rubber nipple inside the cap (see picture) this will allow the vent screw on the cap to release pressure, if not the tank will swell until you open the fill cap which is a pain. I wanted a simple system and not have to lift a fuel tank off the roof rack and then try to pour fuel out of a spout into the vehicles fill neck. With this setup all I have to do is connect a fuel transfer hose to the tank, open a valve, then squeeze the primer bulb a few times and let the fuel transfer. If anyone is interested let me know and I will list the parts bought on Amazon to do this. Also you cannot use the marine fuel quick connectors in this system the fuel will not drain from the tank.

I’d like to see it and any pics you may have. Thanks