I can only ever remember running a 95 spur on my Cougar/TopCat back in the day.... I can't ever remember having issues with getting that to mesh with any of the pinions that I wanted to use.....
Having said that the hottest motor that I ever fitted was something like a 14t double so pinions never went too small. If you are running brushless then gearing would generally be higher than what the manual suggests for an equivilent 'brushed' motor
