I tend to like having a colony on one of the moons of the gas giant where fuel can be offloaded. That way if enemy ships are about to destroy my fuel harvesters, I can at least save the fuel. So essentially, I design a ship like an immobile sorium harvesting platform, but with one civilian engine. I still tow them into place, but allow them to move under their own power to dump the fuel and return to the gas giant.