There really is "no free lunch" on this one and every solution involves some sort of compromize.  The main drawback I see with the Hanibal carrier is that the cans lay down, so if you want to fill/drain them in situ, you give up a lot of their volume and the 20 liter can becomes about a 16l one.  But standing them up on the roof rack takes extra height, and with as heavy as a filled fuel can is, any way you can get them lower is lots better.  For in-situ fill and drain I also like to angle them a little to make it easier to either get the last drop of fuel out, or leave a known settling point for debris, as appropriate for your supply quality.

The "panier" style like AMZ uses is great for accessibility and keeping the cans upright, but is better suited to open area driving I think.  I'd be afraid I was going to rip them off squeezing by a tree.  And better for off road driving because although there's no regulation against it, it still seems a little unorthodox to have possibly 20 gallons of fuel hanging out in space like that when going down the motorway.  A slightly better situation with diesel than with petrol though.

Since my G has the ambulance doors, my original thought was to get a second spare tire carreir, modify it to mount behind the left hand door (spare wheel is behind RHS), and hang a 2-can carrier from that.  A secondary thought was to do the same thing using a replacement left rear bumper as the basis for the swing-out rack.

Of course, if one looks at accident statistics for road driving at least, you're lots more likely to be hit in the rear than in the side, statistically speaking, so that would say put them on pannier style rather than on the rear door.

Lots of options.

How's this for a fun project......build a G that incorporates every conceivable method of carrying extra fuel ALL AT ONCE!  Cans on the roof, cans on the sides, ahead of the front wings like LR Doormobiles did it, long range tanks underneath like offerred by the Ausies and Germans, heck, even throw in that monster fuel cell in the load space like the Dakar G's had in the 80s....Combined with a diesel engine to make it marginally less dangerous and for better economy, I wonder what the maximum range without replenishment could be for a G?  :bleh:  

-Dave G.

I just noticed that the spare wheel portion of the carrier in the picture is actually on rollers and can be pulled out and dropped down on the side of the truck for access.  Now that's cool!  Really necessary for something as heavy as a wheel, but it would be equally cool to handle the fuel cans (or a big Pelican case for that matter!)  in the same way.  Have a pair of them on each side that lay on their big side while on the roof, but pull out and down to stand upright on the sides of the truck for filling and draining.  Fun stuff.

-Dave G.