This for Cliff re the pictures of the rails. : I notice the rusted evidence shows the rusty members are the same round tubing on both the rail sets. Did you have a look inside the box tubing of the other members in these sets?
I wonder how the box tubing fared with the rust problem,? Or did you just accept the inevitable diagnosis that since the round tubes were so badly rusted, the square ones must also be impaired by rust and should be replaced too?
Dave