I have a rudder for a foiling cat in my shop right now.
The bottom skin is entirely missing and the bottom six inches of the vertical fin is split open.
I just sat staring at it for about a half hour and I think I have a reasonable plan to rebuild it but..WOW..it just couldn't be much more fucked up and still worth rebuilding.
If I had a mold. I would simply build a new one and be done in a couple hours instead of taking all day.
I'd be sending that back to whoever built it.