We’ve never actually flown without the slats, they’ve been on the same channel with flaps since day one. I want to say I set the throw at 1/4” and 1/2” measured at the inboard end against the fuselage, will try to check it for you next time he brings it out.
I think the failures that that have occurred have likely been due to a clevis coming off, as it’s damn near impossible to get a keeper sleeve on them. In hindsight I would have swapped out the hardware with 4-40 just so I could use Sullivan clevises with keeper clips. Using the supplied 3mm clevises I tried to slip a piece of tygon over them and had the tygon slip off on the inboard pushrod and the clevis popped out of the horn. Only noticed because the gap was slightly uneven when getting ready to fly, so I ended up getting some safety wire around the inner clevises on each wing as the keeper instead of tygon. I may very well take them out entirely to replace with 4-40 next time it’s down for some maintenance.