I like the idea of smaller battery pack. Already LiPO's have a capacity advantage by making use of voids that cylidrical cells create.
Do we really need 6000mah LiPO's for 5 min races for any racing class?
If the mod racing was able to get by with 1500mah few years back, I am sure they can get by with 2000 or 3000mah.
Used to be racing was about proper gearing and smoother driving to finish a race without dumping. Now racing is about maximum motor rollout and the only worries are if the motor is going to fry or not.
Besides a smaller LiPO maybe lower voltages wouldn't hurt either. Across the pond in Europe they are running 5-cell. Pan cars are running 4-cells. Lossing up to 150g in battery weight can make the cars more durable. I have tried a 2300mah 6.6V A123 pack in my oval car. Even with exactly half the capacity of my EP4600's 4.8V pack, that pack lasted a strong 8min befor dumping on a 13.5motor.