Interesting. I ran a 88/47 combo yesterday and got it to mesh fine (although I was almost all the way left in the motor mounts). I might even be able to mesh a 46. That would be it though - I like the 88 for gearing my 17.5 (requires any where from a 3.5 to a 4.5 FDR). 96 is a great spur gear for 3.8 ish and up for 17.5 or 13.5 from my experience.