Here is my experience with the same issue.
I have two tanks, port and starboard, with a crossover line. After a cruise, the boat listed to port, and wouldn't return to level. I filled both tanks, and it still listed to port. So, I added 60 lb sand tubes on the starboard behind the galley cabinets until it leveled. It took 180 lbs. If the boat is unbalanced, the crossover will not level it by itself.
Still, after a cruise, the boat listed slightly to port because more fuel was getting returned to the port tank than the starboard tank. There is a manifold, but it doesn't seem to balance the flow rate to each tank, plus, the generator returns only to the port tank. I'm not sure what I will do about this. There are shutoff valves on these return lines, and I could shut down the port tank valves very slowly and see if the flow rate to each tank can be balanced that way. Has anyone experience with this approach?