There was grumbling about my 5oz. light, 13.5 car being too fast for stock, so I got the "add weight or die" ultimatum from the guys. Nobody cared when I was losing. But oh no, you have a single night of success, and suddenly you're a big, terrible cheater! :-D
Anyway, I managed to get it up to weight with the Platinum LiPo, but it was a little more difficult than the Carbon version. I lined the top of the pack with flat tungsten weights, and trimmed the foam inserts to handle the additional height. There's a spot toward the back of the battery where you can't add any height or it won't clear the rear bulkheads, which is why I couldn't put the weight down low, under the battery.