I was just looking at the custom slide cover plates at glock store and read that they're made of aluminum, I'm not sure how they put the designs on them maybe laser engraving but my question is, Glock says that everything in them fits metal to metal and plastic to plastic. If this is so then is there any problem installing an aluminum cover plate against the firing pin spacer sleeve and the spring loaded bearing which are both plastic? I see that the stock one is plastic covered with a metal insert.