I have a quick 17.5 blinky gearing question. I know a FDR around 4.0 is a basic starting point but is it better to achieve this ratio through a big spur and pinion (like 105/51) or a smaller spur and a moderate sized pinion (like 92/45)? I believe that I read earlier in the thread that if a spur is too small, it will interfere with access to the motor screw. Is there a point where the gearing won't fit on the car?