I have the Rhino Rack Pioneer platform. Rhino rack sells a bolt kit for Rotopax mounts, they're pricey. You can piece one together with a channel nut and a bolt much cheaper. The thin Rotopax 2 gal water jugs work well, thin enough you can still strap a roof bag and other stuff on top of them. The Fuel cans are tricky on the roof laying flat. They swell and make it difficult to unmount, but it works and hasn't leaked in 3 years. Also, rotopax has an extended mount so you can stack the cans on top of each other. The pioneer rack is rated for 290lbs dynamic and 530lbs static, so you could set it up with 2 gal water and fuel cans on the first layer, then strap your tent, cot, and waterproof roof bag a top...I love these types of racks, good thread! It wasn't until I was messing with this rack and the load limits, I learned that water weighs 4.34lbs a gallon and gasoline weighs 2 lbs a gallon. But I also just learned that pant zippers flip up and lock... 44 years wearing pants, had no clue.
