After all the 'burrowing' was done, I mixed up epoxy with fillers and used this "putty" 'and fiberglass fabric to both fill in and reinforce the missing plywood areas.  As you can see, a huge chunk of the stem was gone.  The area where the plywood was fastened seemed to be in good shape, so total stem replacement was not necessary.  Honestly, if this boat needed a new stem, I'd sooner have a nice "beach bonfire" with her and send her minerals back to earth, then start from scratch.  New construction is quite a bit easier than this type of repair.. but we perserver.....

Here is it all prepped.  The areas of bare wood have been treated with epoxy which really hardens things up, and waterproofs them.  I had to trim the stem back to good wood before shaping a replacement patch.

This is the "patch", ready to go in:



Monterey Cypress stem patch;
very decay resistant and lightweight



Scrape then Sand the whole interior, then primed.