I use this battery:
It's only 950 mah but lasts around 50-60 minutes with a set of Sanwa SRG BLSV2 servo's on high response mode. It's important to set the end points right, otherwise the servos will draw a lot more current.
Because the exhaust side of the car is already heavy compared to the servo side with low-pro servos I wanted to use a light battery.
It's also pretty thin which allows the battery tray to be lowered by 2,5mm.
With the somewhat heavy Hipex low noise exhaust I use I have to add 50 grams to the right side to balance the car.
With a normal exhaust I think it will balance out almost perfectly.