Turbosimi :
Check my blog, I talk about hop up I use and some mod I made.
I also use Losi shocks, check my set up
I think you bought also a bearing ball kit, so, after the shock, the important hop up is the optionnal motor plate, really stronger than the stock one !
Well, maybe the alu hex, very good to use, but that's all you need to make the Mad Rat a competitive car.