You can try the 2S packs, but the problem you're going to have is the less voltage, the more amps you're going to pull (especially if you gear it up to get the speed back out of it). I would personally go with the 3S and think it would be your best shot at making this setup work. Worse case scenerio, you can easily sell a 3S 4000mah 20C pack to anyone that has an electric Stampede, Rustler, Bandit, etc that wants to go 60+ mph....LOL
