That's where running wider-pitch gears comes in handy -- the teeth are taller as well as wider, so even if you can't get a *perfect* gear mesh due to limitations in the motor-mount adjustment, you can still get an *acceptable* gear mesh. 48-pitch (aka Mod 0.53) gear teeth are about 0.35mm taller than 64-pitch gear teeth, which means you can get away with having the motor positioned about 0.7mm further away from the spur gear than is ideal, and the gears will still mesh well enough to drive the car. If you can make the jump to Mod 0.6 without losing the ability to get the gear ratio you want, you can get closer to 1mm of leeway in the gear mesh.