IIRC, the slide stop spring on those guns is a bit like the Walther PP. The spring is a wire V type with one end straight and the other having a rounded hump. The straight end sits in a slot in the inside of the slide stop, with the point of the V to the front, and is staked in. The humped end then is sticking up and when installing the slide stop you have to use a small screwdriver or something to push it down so it will go under the edge of the hole in the frame above the trigger.
If that does not make sense, please post a photo of the setup on yours, and we can try to help you figure it out.