One other change we made at the nats was to change from ceramic to carbide diff balls. The theory is that the carbide diff balls have a higher coefficient of sliding friction against the diff rings, meaning less pressure (tightness of diff nut) is required to keep the diff from slipping. This did seem to be the case on Jeff's car, and we were very satisfied with the performance of the carbide balls. Worth a try if you are experiencing slippage issues.