I was wondering of how to make resin reinforced, and I forgot all about additives. Try adding powdered stainless steel into your batches. It makes it thicker, and pastey, but it really does add a lot of strength. A better material is Aluminum. Usually, can sometimes buy it from stores online 5 pounds for like 30 bucks. I know some people even mix it into their paints. They use it in cold casting also. Try adding it when building up your chest armor, and other large flat areas where it doesn't need a lot of flexibility. The more layers you add, the more metal-like it will get. Adding it to your bondo works also. But experiment with a small quantity first before right ahead of application. Sometimes you need to decrease hardener for more flexibility. I used to use epoxy-steel combo to fix cracks in all kinds of stress ridden metal. It works pretty darn good. For the most part, and permanent too.