Savage XL Brushless project

[rcBOB]

Hi everybody ! I'm now the owner of a brand new 1717 motor !

So, i'm going to buy the kershaw's direct drive for my savage xl but i don't know which pinion to choose...

I've seen the gear ratios on kershaw's website but they're made for Castle creations 41,8mm diameter motors and i've got a 50mm diameter motor !

As you can see i don't konw what to do...

Does anyone can help me please ?

Thanks.