Question On Weight Distribution.

Is it better to put the weight on top of the servos or for the servos to pull the weight? I found a good size piece of Styrofoam I'm going to use to make a new bot. (3rd times the charm!) but how i utilize it depends on the question I pose. Witch way would cause the most strain on the servos. I'm using the modified servos from my ezb complete.

It's not much weight but it's definitely top heavy. I just want to know if i should pull the weight since the ezb and stuff will go into the hollow lighter side and it will balance out better or if I should put that weight in front on top of the wheels?

Thanks in advance.