A side issue to mast base replacements...

The likely way the mast base attachment rivet areas fail is during stepping. Be sure that your mast step link directs the base into the step casting properly. If the link allows the base to hit the step forward of the cup, you can leverage the base out of the mast. That rips either the mast extrusion or the base casting at the rivet locations. Another way to avoid this damage is to slow down the stepping process when the mast nears the upright position, pull back the the lower end of the mast to be sure that the base drops into the cup.