I think Your pretty close B4racer.....the rest is really trial and error......also if you cut and rebuild the motor over time, the ideal pinion size for a given track will sometimes change......a comm with more cuts will yield higher rpm and a big or new comm will lend itself to having more torque....as you mentioned batterys can have a effect also....a very good pack will sometimes allow you to gear up...something also that might help that alot of people don't get the concept of ,is that you dont nesessarialy gear down for torque and up for top end.....its not like a gas motor, an electric motor has a near instant powerband....and that changes everything.....hope this helps some