Originally Posted by DS Motorsport

Your right on one part, but wrong on another part.
Adding more material doesn't automatically makes for a stronger part.
Adding material in the right spot, makes a part stronger. Sometimes you could make a part stronger by removing material, because the material doesn't add anything to the structural integrity of the part and only weakens it because of the added weight, so more stress at high rpm.
I have a JP engine which has the intake side of the piston milled away from the bottom of the piston to the bottom of the piston pin.
Makes up for a much lighter piston, but it doesn't weaken it.
As a downside, the engine is much harder to tune and was worn out quickly (5 liters) because of the huge power and high revs.

The main thing to improve, especially for 2.1cc engines, are the bearings.
With the current high tuned engines they last 2-3 liters at most in high competition.
Another important thing is crankcase rigidity. You would be amazed how much the older crankcases flexed under high load.