I have three bars on the truck that bent a bar, and I'm adding a fourth bar as part of the repairs. That assumes that I can find a pair of the discontinued towers on my setup.
The other truck has a two-bar setup, augmented with a Yakima DryDock in the hitch. I carried a 950-pound load of lumber, up to 22-foot timbers, and managed to bend a bar in a 60-mile drive. Grossly overloaded? Absolutely. But everything survived except the bar and it's ugly but still usable. If I had distributed the load differently, the bar might not have bent. The towers seem to be able to handle a lot more weight than the bars can. And still no leaks from the track.