Couple questions..
So on my carpet knife the left side of the axle sticks out almost 11mm past the hub.. seems to me I should just cut it off rather than have the motor spin something the car doesn't actually use. Sooooo, should I?

What is considered a big jump in rollout? Say I'm running a 3, and jump all the way to a 4, I'm guessing that would be a big jump. Would going to a 2.75 or a 3.5 be a big change?

I'm used to offroad vehicles where you just try pinions until you get the feel you want and then basically leave it alone until you switch from a long track to a big track.

I read from one of the links earlier than a 2mm change of tire diameter can be like a one tooth change on the pinion. I guess if that is true, than I can just calculate two rollouts with one tooth pinion change and see how significant the number difference is..then try it on the track and see how significant it feels to me.

Thanks for baby-sitting the offroad guy