I know that's what Castle say, but really you don't want more than 4S on either motor when racing. They're referring to bashing, where you can get away with the high rpm.
That battery is an excellent choice, but I'd use a different motor than the 2200kV Castle one. Efficiency is between 28,000 rpm and 35,000 rpm, 2200 x 18.5 = 40700rpm, which will cause the motor to heat up and you will get less run-time. I'd go with the 4S 6500mAh pack instead with the 2200kV.
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