gearing help

[gasshead]

i tired a search but that didnt help me much. i also tried BrianG's page but didnt really answer my question..

im in the process of finishing my revo and all i need is a mod1 pinion, but what size.

i have a MM, 9XL, 38t spur, and 12 cells (later upgraded to a 4s lipo). i also have the wide ratio and CD in the tranny.

what wold be a smooth, fast, cool running pinion. im thinking some where in the neighborhood of 19 tooth?