There are different kinds of LE flaps. Some are simply hinged at the lower edge of the wing ( F 104 ), and some use offset hinges that form the lower part of the leading edge when retracted ( B 707- 707's don't have slats). Boeing calls this type a Krueger flap. It has an articulating feature that deploys a rounded tip as the flap extends. Some airplanes use both LE flaps and LE slats on the same wing ( 727 ). The 747 uses LE flaps which are unique. They are flexible and actually change shape when they deploy. I believe they are made of fiberglass (at least the old ones) and are known as variable camber LE devices. There is even variation in how they are deployed. The 727 slats come out in pairs, the inboards first then the outboards together with the LE flaps. Most newer planes deploy them all together but have different positions. Some are just up or down, and some has as many as 4 positions. My point is that there are many different types, you just have to know what your subject airplane uses.
I don't know of any large airplanes with aerodynamically actuated slats. In fact the only ones that I'm aware of are the F 86, F100, the Sabreliner, and I believe the ME262. Maybe someone knows of others.
It would be nice to hear from more of those builders who have fitted these to their models to see if they consider the effort worthwhile on our models.
Paul