The manual instructs you to tighten the slipper so that .5mm of the shaft is sticking out past the nut. I always start there plus a quarter turn.

For the diff, you tighten it in increments of a quarter turn. To test your set up Break in the diff per many of the guides found on the internet, then place the buggy on a table and hold both rear wheels down. Blip the throttle on your radio. What happens? If you hear a barking sound and can feel grinding when you hold the wheels then the diff is too loose.

If the front wheels dont come off the table at least an inch tighten your slipper a quarter turn. Check again and adjust until the front wheels come off the ground about an inch or two for loose tracks, and 2 to 3 inches for high grip tracks. Works for me.