gearing for brushless setup in slash

[RydeFab]

just wondering about the guys that are racing their slash's on a short track and for bashing. what pinion would be sufficent enough for mine with a mamba 5700 set up with a 8000 2s lipo? i'm planning on using the stock spur and getting a 90 tooth one during the week. i haven't thermo'd mine yet, but with the 6900 i did. i'm using the 2 pinions that came with the truck. i've read that some people have gone 2 pinion sizes up and down. i'm just wondering what would be a good starting point before i start experimenting.

as of right now, i'm running the stock spur with the bigger of the 2 pinion's that came with the kit. after about 10 minutes of hard bashing the temp was at around 185 degrees at the motor. any input on this would be great, thanks alot.