Welding is questionable. They end up cracking at the weld. We had a guy who had his corner castings tack welded to the crossbar for stiffness... broke the crossbar (at the weld). There is a lot of twist in this part. A weld likely concentrates the forces as it would not give at the same rate.

A replacement crossbar extrusion runs $234.70 including a new mast step casting. Would have the integrated traveler tracks too.