I put Kenny Kong's metal tracks on my Tamiya Pershing back in 2004 and it is still rolling along fine. They add quite a lot of weight, but don't worry. The Pershing's drive and gears are designed robustly enough that I have never had a problem. It maneuvers through all kinds of terrain without fail and I think the extra weight helps it ride and move in a much more realistic "tank-like" (read: heavy) manner. Many of the guys here consider the Pershing to be Tamiya's best engineered tank to date.