Legal or safety issues carrying diesel fuel containers in RV

All conjecture aside, use the steel safety cans. The "typical" plastic cans will permeate through the material and put out odors. The metal cans don't do this. I've carried diesel fuel around in the back of my truck (with a rolling cover) in hot temps and nary a smell of diesel when you open the tailgate. The safety cans also are "safer" and they won't fall over, bounce around, etc.