an 1/8 to a 1/4 turn is a lot for a slipper clutch. when i adjust the slipper on my XXXT i have to do it about 1/8 to 1/16 at a time.
the thing to do is to tighten it down all the way (be careful not to go to tight and strip or damage it) then back it off about a half turn or so and drive it around on a flat surface. test it and back it off (or tighten it up if you have to) a 1/8 to 1/16 of a turn. test it. and keep doing that until it slips the way you want it to. should take you all of about 5 minutes to have it dialed in where you want it.