What other metal parts do you have as things such as road wheels and suspension arms not to mention most of the track are un-sprung weight so don’t really count things such as sprockets and idlers plus about ¼ of the tracks are sprung weight and by adding more sprung weight affects the suspension, if weight is so important and I can’t see why it would be as it would add more problems why not simply buy an all metal model and if you really must add more weight