Mamba Max pro in a mini slash?

I am no expert by any means but from my understanding it is the motor (gearing too) that will determine the current draw. Since the original ESC is way weaker than the MMP I think you should be fine. The only thing that might be an issue is the Ni-MH batteries. I wouldn't use them. They are not very kind to the ESC and their performance is dismal when compared to lipo. The only other issue you might have is fitting the MMP to the mini chassis. Mot much room there.