I was very disapointed with the quality of the plastic in the stock kit. When i'd lift a corner, the chassis would twist rather than the suspension move. I... now understood why it came with crazy stiff shocks. The actual suspension was the chassis.
Tamiya, and 3 Racing both sold carbon chassis kits for this car. I suspect they won't actually be lighter, and... there is this thing called a budget. And I planned on keeping this thing pretty cheap. Tamiya also sold all of the kit plastic in carbon injected form.
Tamiya claimed the parts were lighter than stock. On average, I think I saved a gram. But the parts varied from 1-2g heavier than stock to 5g lighter than stock. With no real rhyme or reason. Total weight savings, not including that aluminum shaft, was 9 grams.