thanks for the input guys
I tested the car outside my house, and the car is more punchy with the 4200s(duh). But the car is much more nimble with the 2400nimh. Not sure if anyone tested, but is there an optimal weight for TC for the type of tires we use(asphalt with sorex36)? If it is too light, there won't be enough weight to maximize the contact patch. Maybe a 3000mah batt is better for overall balance(weight, power, runtime). BTW, the car weighs 1380g race ready using the 2400s.