Got the 4s lipo, only weighs 80 grams more than the 3s. I was very excited to run it, however ended up a little disapointed. Im running on grass now and have lots of grip, I kept the gearing the same but the power is SO much I couldnt stop it from wheelying, over the full length of the field I couldnt get to full throttle, the front kept poping up and when I pushed this ended up in a massive cartwheel (20 rolls easy). The truck survived all the crashes intact! which I was surprised at, the motor still cool, but I couldnt push really. The center diff got up to 150f ! it was really working hard, im going to try reducing punch on the mamba but i'll probably end up going up a tooth on the pinion and going back to 3s.