I got my plastic spur today so I was able to change out the steel gear on my smart diff. I Installed the diff (center) and took it out for a spin (street). It definetly feels like it hooks up better, driving on the street is actually a good test because there is so much more traction. Off power turn in was great. The brakes felt good and seemed to stop like they did with the stock diff. Below are some pictures of the inside of the diff, the smart diff inner parts will not fit in the standard diff case. Also a slight issue using the plastic spur, it is a bit wider than the steel spur, and at first there was some binding with the motor mount. After a few runs up and down the street it freed up and felt fine. I hope it stays dry this weekend so I can get some track time in.

Losi Smart Diff and plastic spur gears.

Inside the Smart diff.

Plastic spur is a bit wider, some of this extra width is on the motor mount side and binds slightly, until the high spots wear off.

You can see how close the plastic spur comes to the motor mount.