For those brave souls interested in making their own rudders, I'm uploading the photos I took with the dimensions in wax marker on the sides of the old one that snapped in half during our grounding.

FOR ALL, NOTE:  The lateral SS support strut inside the rudder was clearly low grade SS and had suffered serious rusting (fresh water only!) from water leaking down the shaft inside the foam.  The PO did not mention a prior break in the rudder, but the split in that strut (note the rusted edges of the split SS) MUST have happened previously and had been repaired.  (Might have happened when the vessel was rammed from behind while in its slip and suffered damage to the stern portside quarter, professionally repaired.)  Point is NOT that the split had to do with the rust, per se, but rather that the rust leaking out of some small cracks in the rudder was NOT from the SS post, but from the strut inside.  If you have rust leaking out of your rudder, this is the likely source, not the post.