Which is why I race 540 stock (or will be anyway) in NZ Johnson 540 motors and 1500mah unmatched stick packs.
Personally I don't think the extra money for that higher capacity pack is worth it the race is still 5 minutes and there's usually no more than 2-3 laps between the best mod and the best stock time anyway.....
with the bonus being it's easier to get the car down to the weight limit.