So the real answer! I have no idea!! Drove it home, after we installed it, on the highway. And have only driven it down a couple forest service dirt roads so far.
But, my thoughts on off-roading. BTW- i have a crawler and another 08runner that i love to drive fast around the desert.
My Tundra is not a desert racer. This means i drive plenty fast and bomb down fire roads, desert washes, forest service roads, and tons of desert 2 track and washboard roads. Always in pseudo-control and if something huge comes up i slow down and navigate thru it. I drive nasty sections with big rocks, or steep rocky sections, at a very slow pace in control where i can choose my path and choose where the truck may make contact.
The Tundra is a long rig and its easy to drag over the top of a berm or wash as you cross over it. Or scrap along a large rock with the sliders or framerail on a corner boulder. OR maybe i even drag the rear axle over a large boulder that i couldn't get around.
The idea of slamming down very hard on the tank under all these situations is HIGHLY unlikely. Ie- puncture or massive crumple.
Likely in a bad situation i may have to drag over a rock or across some small short obstacle with the tank. Its 12G on the bottom so somewhat durable to allow it to hold up sliding gently and calculated over said issue, and if its sand or grapefruit rock the coating should even hold up fine. If i was that guy that hucks his nice truck in the dunes- no issues. If i ws gonna huck at Ocotillo desert with rocks- this tank might be a bad idea.
So, my thoughts are the extra gas is massive. The likelihood of destroying the tank because it sits just under the framerail is very slim. Something to be cautious of on super nasty, gotta choose the right line. But its not a big anchor ready to catch on any little thing, its gonna be obvious.
Did i blab enough?