Support for Bracket

[Andre205th]

Hello all.
I plan to add an outboard bracket to my B25. What kind of support do I need?
I've already replaced the transom bump out core with the same thickness of Coosa and 3 layers of 1708 over the bump out. Glass extends 8 inches or so past the bump out in all directions and onto the stringers.
Andy on boatworkstoday added several large patches to the corners of his transom, that's doable.
What about tying into the stringers with vertical stiffeners and glassing to the transom, like the Bomber B25 on this site.
Will 12" strips of marine ply glassed flat to the inside of the transom wherever the bracket is through bolted work? Aluminum or Coosa instead of ply?
Thanks