I'm a big fan of the larger fuel tank and a small rotopax on the spare tire. I've got reinforced hinges and that's a setup I like a lot, though I only use it for water and I've never used a rotopax fuel container, but likely will one day for the wife's Tacoma.
From there I would suggest keeping the weight centered and low. My preferred gas can is the actual GI heavy plastic ones, but I've been told they blow out the seals prematurely if you carry them with gas. The Race cans are my second favorite can (would be my favorite if I couldn't find the GI ones for $15 locally). From there I like the nato looking plastic scepter cans. I have a small metal jerry can I use for mixed gas that I like, but in practice I've never liked those cans for gasoline, but I've only had the cheap versions, so it seems like the ethanol does a number on the inside of the can and the nozzle always wants to leak really badly.
And if you don't like spilling fuel and taking 5x longer to drain the can (I've timed it, but don't remember the exact time), don't use the EPA/Obama spouts. When you use that style of spout when you really need every drop of fuel it's very easy to litter after you've spilled a bunch of gas everywhere but inside the gas tank, by throwing the spout angrily in the woods while cursing loudly and you get to smell like gasoline the rest of the day. So make sure these get into the trash before you go out and modify your cans before you need them and make sure the spout is long enough to get the fuel into your tank.
I make my own spouts for the GI cans and make them a little longer than the race can type. I make the last little section compatible with whatever NPT threads they use on the race cans (I think 3/4 NPT), because the added length of hose is preferable to me. My spouts are just a couple of PVC adapters and then some clear hose.
Though I switched to diesel, I do have to carry gas, because gas engines are always very thirsty, but it's normally just generators and small equipment we've got. When I run our gas tractor I pretty much have to bring a trailer to keep that tractor gassed up (it's a small tractor too). The better solution is a plastic drum on a trailer. For diesel I prefer transfer tanks in truck beds.
Throughout the years I've used those hitch carriers to carry fuel cans and they work ok, but I do bump them fairly often when I'm off-road. I got a raised one, but then I can't open the tailgate very far even when the thing is empty. It does work and it's not a huge deal unless I've got my dog with me. The roof is now preferable IMO to the hitch carrier. There's a big container made to go around the spare tire, but I haven't tried it.
