I have an original stadium thunder and this came with a 13t pinion gear and a rs540 black sport tuned motor. I want to upgrade the motor however in the instructions do not give an option for any other size pinion to be used. Can I put in a 27t dirt tuned motor?. Also the standard rule I thought was to use a pinion gear two teeth below the motor so for 27th this would be paired with a 25t gear. With this rule in mind why would tamiya use such a low gear for that motor?. Also if I put a brushless 15t motor in could it handle it and again what pinion would you use?