I recently bought an early Gotz who had some armholes that were on the point of  tearing on the body side of the armhole.  The metal hook was rubbing on the soft plastic of the lower part of the body armhole.  So I had some rubber soft tubing that I used to cushion the hook.   Here are photos of what I did.  This maybe 'old hat' to Sasha repair people but I thought I'd share how to protect the armhole.  Here are a few photos to show what I did.