cant speak to the larger roto Pax tanks, but like I said they are stackable. At some point you gotta do the math. My 3.2 IMS tank I think was 240, still not enough for long days, but perfect for 75% of days. So if you spent that on spare fuel storage your ahead of the game, no modifying fuel lines, pumps, plastics, etc. Not to mention the ability to carry that weight low. 3.2 is fat, side panels don't fit all that good and catch branches because they kind of hang out there, already broke one. I personally would not do it again and would opt for a bada## spareI concur with Ishartd about tie down risks. A novice friend of mine showed up for dirt biking with his ratchet tie downs (hate those things). I made him return them for the cam-style just because the buckle is lighter. By the same token, no strap at all is even better if you have something to lock directly to.
I'm going to look into those Roto cans but it seems 1 gallon is a little too small = 3.8 litres. Canadian Tire has a 5 litre Scepter can that fits between the rails perfectly. However, my KTM 300 has an 8.xx litre tank so if I run down to reserve I want to be sure I get back. Two gallons gives that assurance = ~ 7.6 litres. Does this Roto brand have a 2 gallon that would fit well?
fuel setup.