Novak states that you can run a 3.3 FDR on the 25.5 motor which means you can go to as much as a 55 pinion. You probably don't want to increase the timing much at that and you could raise it at your current FDR which is about 3.5. Make sure you check the motor heat every two minutes and keep it under 170! Less timing gives you more torque and higher timing will give you more top end. Find a happy medium that works for your track.