Adding the Strap
First, use rough sandpaper on the back. This will help the glue stick better. I had sprayed my plastic with a clear coat, so I also wanted to scrape that away for better adhesion. I aligned the strap, and put a few drops of super glue to hold it in place. Then I mixed up the 2 part epoxy and spread it underneath the strap, and let it harden.
Then I added another layer of epoxy on top of the strap, to completely bond it. Finally I added the two strap braces of plastic for extra reinforcement.