Why are you dead set on running a Stampede on 4S? It is not going to run well on 4s, no matter what motor you put in it. Nobody is going to tell you "yeah, go for it". All it will do is wheelie. This is a stock Stampede chassis on 2S with a brushed motor. Even with a Castle 3800kv with 2S, it is...
If you're lucky, it will only bend the arms. Likely the shock of an impact will transfer to the hinge pins and bend or break things farther up the mounting locations. Aluminum arms are really only good for shelf queens. It's not so bad on lightweight buggies and such. But on a monster truck...