Alright guys, I'm researching tire carriers but I keep bouncing back and forth on this. Rotopax are lighter and have more mounting options, but jerry cans are stronger and hold more.
Consider a small one for water. Plan your trip based on gas consumption. Best I got crawling was 7 mpg. With a big group even less due to waiting time. Most off road parks have bypasses you could exit without crawling through. Having said that 3gal should be enough.
Off the trail do not carry a jerry can full or empty. It is easily stolen or damaged and it is hazardous. Plus if your not using the gas it may collect too much water to be useful.