Trasom repair from the outside...

[tsubaki]

That is the classic way to replace the transom. The few people that I know about that have done that or acquired a boat that had that done complained about the joints cracking because of the stress. This is not to say that this method is good or bad. Most likely it is related to the quality of work and not the method. As for me I don't like the idea of cutting factory molds unless absolutely necessary. :-/