Any weight you add to the car should be down the centre.
It's basic physics.
Imagine two axis,a Y and X axis,one is straight up the centre of the car,the X across the car.
Your cars weight in all four corners will always differ when the car is being driven,but,as long as it can ROLL from side to side,the car will feel great.
Adding weights to the edge of the chassis is creating a ballast effect,the car HAS to expend more energy hauling that weight around a corner,whereas in the centre it's all evenly distributed.
You will be creating a pendulum effect and will upset the whole dynamically set ups made to the car.
I really advise you try it though,put ALL the weights on the corners and see what the car does.
Do this when your on the track on your own as it won't be pretty.lol.
Hope this helps mate,corner weights aren't critical on a moving object.
Tim