GP3300's are close to the same price as 2400s and are definitely better. I'd go with side by side packs though, and if you can't do it yourself, someone at your track would be willing to assemble them for you. Side by side packs sit lower in the car than sticks so you have a lower center of gravity, and thus your car handles better
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BTW, side by side means the cells sit side by side, they are all in a row, so to speak.