The stock CRC is pretty good, the Z flex really lives up to its name and is like trying to bend a piece of steel. The only issue with it is that in order to use all of its features and the two tungsten weights installed under the battery, you have to really fight to get the car near the lower weight limit. I know that sounds dumb... "Well yeah, you installed ballast and its overweight? No shit." You can use the ballast and get it to weight, you just need a light ESC and plastic case servo. I used neither of these, and had a fan and a capacitor bank to keep temperatures under control, so I'm 25g overweight even without any steel hardware.