Container's air tight, I know because I had to burp it periodically when changing elevations in warm weather to restore the can to it's normal size.
Held on by bungee cords (three of them) so that in the vent of an impact the jug would likely be tossed free and away from the lane of travel.
Given the height of my cargo rack from the ground, if I hit a deer, it would likely bend down and act as a ramp to drive said deer up into my windshield.
I carry 30 gallons of fresh water, 5 gallons of gas (opposite side of the furnace, water heater and fridge on the camper), my firewood box (full or empty of old lumber cut offs from the local mills, depending on where I am traveling), a splitting maul and a small bbq on there. Directly behind which is my spare tire on its own independent mount.
If I get rear ended, if the 48" double walled hitch extension doesn't prevent an impact, I'm pretty hosed anyway because the two 20lb propane bottles sit just above bumper level in their compartment as per the factory design of the camper and my gas generator on it's mounting basket on the rear left.
So, I try my best to be sure that I'm paid in full with the man upstairs before embarking on any journeys :p.
