Pics of the battery stopper mod. All of this was done with Pro4 servo mounts and the fan was done with TA02 servo mounts. The fan mount allows tilt and angle adjustment and if needed, fans can be split so one blows on the motor and one on the esc.
The battery has been moved so far that I had to use a soldering iron to melt part of the battery strap so the corally plug could go through! Like David Galdo said, the car is pretty much balanced when the battery is this close to the centreline of the car (assuming you are using the newer heavy Lipos like the 5500-6200). If you are using older batteries like 5000, the car is already pretty balanced in the standard position as the battery is only about 265g heavy.