InspGadgt

If you track set it just to the point where it does not slip under hard acceleration from a dead stop then pick it up, hold both wheels in your hand and turn the spur with your fingers you'll find it does still slip, not easily but it does. But since it does not slip on the track this gives you the most free diff possible. This brings up another point that your diff settings may even change depending on motor.

I haven't tried the Corally but I have tried the Slapmaster. Jason pointed out the difference between the Slapmaster and the stock setup at the Birds which I had not noticed. For club parking lot racing the Slapmaster was working just fine for me but at the Birds I wasn't getting enough turn in because my diff wasn't free enough. I looked it over when I got back home trying to figure out why that was...one thing I thought of was the washers...with the slapmaster running concave grooves in the washers more of the thrust ball makes contact with the metal which is going to increase the amount of drag on the diff. Additionally if it has to do more with the direction the force is applied on the thrust bearing vs the outer hub bearing maybe something like a conical thrust bearing would work or it could be as simple as using a larger bearing race in the hub to increase durability.