The first time we did Maze District (Canyonlands) we spent 4 days and went to more campsites. Panorama Point, Maze Overlook, China Stairs, Doll House. Many of those are basically long out and backs. Days spent driving many, many hours a day in low range. We filled up at the last gas station in Green River, had 10 gallons of gas on the roof, put all 10 gallons in, and hit Hite UT with under 1/4 of a tank. Where they know you probably don't have much of a choice and charge accordingly (hah).
The last couple of times we've gone to the Maze District again, we've streamlined it a bit, only needed 5 gallons.
Rather than sticking gas cans on the roof, I was considering using EMKeith's mounts and putting a Ford tank in the back where the spare used to be, but leaving the Toyota tank in place. And just using the pump in it to move gas from it to the Toyota tank. Flip the switch, turn off when the Ford tank goes empty or the Toyota tank gets near full. Fill is using a dual fuel neck behind the stock gas door. It would be nice to not have gas in plastic cans on the roof getting baked in the sun (they bulge like balloons). It's jsut a lot easier to strap the can/cans up there occasionally when you'll need them, vs. spending time and effort to put that Ford tank in. But it would be handier, and keep the weight off the roof and way down low.