Sorry for the delay in posting more pictures. It's all done and feels like I'm walking on concrete - VERY solid. ALL wood (marine ply) was given a few coats of epoxy before installing. Overkill, but I'd rather do it that way for the long run. Here's some more pics:
These are of rebuilding the aft bulkhead - the one directly behind where a aux fuel tank would go (and in front of where a stern drive would've been.
This one is of the main "new" piece (cut it into two to slip it in and then glassed the seam). Looking aft:
This is the same piece, but looking forward (and after I trimmed the extra little bit of original glass that stuck up over the wood). I had left it in place since there was no reason to remove it.
This is what I assembled to give this bulkhead more strength. The second and third pics are looking aft, then forward. All edges where tabbed into the surrounding glass.