Slipper setting on cat sx2 and cougar

[Robocop]

Hi
Just getting my cars ready for the season never run the cat yet but how much of the slipper thread is showing on your car.Do you run cars with little or no thread showing will be run on high grip,understand that the diffs will bed in so will have to tighten them up with use.But last year ran the cougar about 6 times or so but i melted a diff did the clip mod diff in both cars are tight but free.
How much slip should they have on astro as a guide?
Thanks