hello if you go up 8 teeth on the spur gear you will have much more accelleration but with less top speed.
Think of it like the gears on a mountain bike,the front gears get larger and give more top speed,the rears get smaller and also give more top speed.
The bigger the pinion or clutchbell the higher the top speed.
I haven't done much with the new carson but if your 40 tooth spur is standard on the car and you go up 8 teeth also then you might not be making the most out of the available torque.
Also check if it runs a gear carrier as that might need changing if you try a much bigger spur.
I hope this helps mate.
Danny.