Durga gearing question.

[Spoolio]

I am running an LRP 7.5T brushless motor and a stock 91T spur. The gearing chart that comes with the motor suggests I should be aiming for either a 12:1 or 13:1 final drive ratio dependant on whether it is being used on a low or high traction surface. According to the gearing chart off the site, this means I need either a 16,15 or 14(!) tooth pinion. This seems way small and TBH the lowest I can get is a 16.

What motor/gearing combo's are you all finding effective while at the same time still being relatively controllable. 4WD is still a learning curve for me.