I would just like to mention that while it does reduce rotational mass and decrease friction, it does INCREASE the load on a smaller area. Since the force is the same (same motor) but the surface area of the gears is smaller, you are putting the load on a more concentrated area.

You would be more likely to blow diff gears or idler gears if you cut them down. If you combine cut gears and a slipper eliminator you will likely see premature failure of some of the internal parts.