Don't take me having a different opinion as I don't value the input from everyone. Sometimes you have to ask the right and wrong questions to realize that sometime your idea really did not make sense. The only reason I even say anything about the corner skins and tire carrier with the fuel as there is a mechanical advantage on the way the weight affects your suspension. If I did use the tank the weight would be much close to COG compared to the way Moby handles that weight out there, and that goes for any jeep using the tire carrier running 40's.
Again thank you to everyone on the input.
I can assure you, my corner skins and tire carrier do not weigh anywhere close to what a tank filled with 20 gallon of fuel does AND it's wrapped around the body - NOT all concentrated at one point, the very back of your Jeep. ALSO, they are fixed in place as in, the weight is always the same and in the same place - it's something you can account for and address. This, as opposed to a liquid that can dramatically throw its weight around and change how the rear end of your Jeep behaves depending on how full or empty it is. While the gas tank might be lower on the body, it is again, concentrated and ALL placed at the very back of your Jeep.
Living out in Nevada, I do a TON of long distance wheeling out in the middle of nowhere where having more gas is something that can be helpful. If having an aux tank were as great as you'd like to believe it is, I'd be running one. For anyone who actually wheels their Jeep, they know these tanks are a liability - NOT a benefit.