to use a lipo you must use a 21.5 novak brushless.
Option 1: 27-turn ROAR stock motor: No FDR limit, bearings are not allowed.
Option 2: 17.5 brushless: Motor timing advance is allowed. 12.5 mm rotor diameter maximum (no "tuning" rotors are allowed).
Option 3: 21.5 brushless with 2C LiPo: Novak SS21.5 Pro brushless motor (pn:3421) ONLY combined with any ROAR-approved hard-cased 2C 7.4v LiPo pack up to and including 5000 mAh capacity. Novak motor is the ONLY motor allowed at this time, because there are no ROAR mandates or restrictions for the 21.5 brushless motors. All house track rules regarding LiPo usage apply. Final drive ratio is to not exceed 4.2. Motor timing advance is allowed. 12.5 mm rotor diameter maximum (no "tuning" rotors are allowed).
Owning a lot of RC vehicles doesn't always mean a lot of knowledge.