Thanks guys.
As for the slipper mod and due to intending to keep the 1st gear of E maxx tranny, I would first try to tighten the stock slipper all the way. If that does not work well, then I will replace the 12 friction pegs with steel balls. I think Revo spec slipper mod is my last option because I am not trying to give up the 1st gear in the tranny now.