Verify that the fuel is at the fuel stop airports. Knew someone that flew to Europe and back in a SEL. On the return flight, while calling ahead to check on gas, he was told "the fuel delivery didn't make it. We don't have fuel for you." The solution was to strap a bunch of plastic fuel containers into the seats and buy some strainers made out of cloth. It was either that or leave the plane and come back after the next avgas fuel delivery was made.