how about there is no damage percentage, but instead, there are points assigned, and steel can have no less then, lets say 20, so, you take some steel to a really good smith, he forms that armor, and also, being the great craftsmen he is, takes the points to 50. Then you go on your way, and enter battle, the armor slowy begins to get worn down, once it reaches an area of around 20, you take it to get repaired, because lets say, if it gets below 20, the steel is damaged beyond repeair and it would be better off to start with a new peice, ok, back on track, so you take it to this smith, but he is no where as good as the first, he takes the damaged armor from the 20s to the high 30s or low 40s, and you go and fight again, and repeat the process, hopefully along the way, you find a good that is EXTREMELY good with steel, however his fee is hefty.